I wasn't able to replicate (ran multiple times locally). But the error failure seems weird to me. It may be a strange race condition that isn't easily repeatable.

**Build scan:**
https://gradle-enterprise.elastic.co/s/qglznapknwmya/tests/:modules:reindex:test/org.elasticsearch.reindex.DeleteByQueryBasicTests/testDeleteByQueryOnReadOnlyAllowDeleteIndex

**Reproduction line:**
```
./gradlew ':modules:reindex:test' --tests "org.elasticsearch.reindex.DeleteByQueryBasicTests.testDeleteByQueryOnReadOnlyAllowDeleteIndex" -Dtests.seed=B36AB6B5F42DB7E5 -Dtests.locale=cs-CZ -Dtests.timezone=Etc/GMT-8 -Druntime.java=17 -Dtests.fips.enabled=true
```

**Applicable branches:**
8.10

**Reproduces locally?:**
No

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.reindex.DeleteByQueryBasicTests&tests.test=testDeleteByQueryOnReadOnlyAllowDeleteIndex

**Failure excerpt:**
```
java.lang.AssertionError: 
Expected: updated matches <0L> and created matches <0L> and deleted matches <0L> and versionConflicts matches <0L> and failures size matches <26> and reason cancelled matches null and slices matches an empty collection
     but: was <BulkByScrollResponse[took=283.3ms,timed_out=false,sliceId=null,updated=0,created=0,deleted=26,batches=1,versionConflicts=0,noops=0,retries=2,throttledUntil=0s,bulk_failures=[],search_failures=[]]>

  at __randomizedtesting.SeedInfo.seed([B36AB6B5F42DB7E5:86367E10FB79DB4B]:0)
  at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
  at org.junit.Assert.assertThat(Assert.java:956)
  at org.junit.Assert.assertThat(Assert.java:923)
  at org.elasticsearch.reindex.DeleteByQueryBasicTests.testDeleteByQueryOnReadOnlyAllowDeleteIndex(DeleteByQueryBasicTests.java:265)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-2)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
  at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:568)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:48)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:843)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:490)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:850)
  at java.lang.Thread.run(Thread.java:833)

```
modules/reindex/src/test/java/org/elasticsearch/reindex/DeleteByQueryBasicTests.java
.filter(QueryBuilders.matchAllQuery())
                        .refresh(true)
                        .setMaxRetries(2)
                        .setRetryBackoffInitialTime(TimeValue.timeValueMillis(50))
                        .get(),
                    matcher().deleted(0).failures(docs)
                );
            }
        } finally {
            disableIndexBlock("test", SETTING_READ_ONLY_ALLOW_DELETE);
            if (diskAllocationDeciderEnabled == false) {
                setDiskAllocationDeciderEnabled(true);
            }
        }
        if (diskAllocationDeciderEnabled) {
            assertHitCount(client().prepareSearch("test").setSize(0).get(), 0);
        } else {
            assertHitCount(client().prepareSearch("test").setSize(0).get(), docs);
        }
    }
    public void testSlices() throws Exception {
        indexRandom(
            true,
            client().prepareIndex("test").setId("1").setSource("foo", "a"),
            client().prepareIndex("test").setId("2").setSource("foo", "a"),
            client().prepareIndex("test").setId("3").setSource("foo", "b"),
            client().prepareIndex("test").setId("4").setSource("foo", "c"),
            client().prepareIndex("test").setId("5").setSource("foo", "d"),
            client().prepareIndex("test").setId("6").setSource("foo", "e"),
            client().prepareIndex("test").setId("7").setSource("foo", "f")