This looks like more fallout from the 8.12 version bump.

**Build scan:**
https://gradle-enterprise.elastic.co/s/iznsqgeozhlcw/tests/:x-pack:qa:rolling-upgrade-multi-cluster:v8.11.0%23follower%23upgradedClusterTest/org.elasticsearch.upgrades.CcrRollingUpgradeIT/testCannotFollowLeaderInUpgradedCluster
**Reproduction line:**
```
./gradlew ':x-pack:qa:rolling-upgrade-multi-cluster:v8.11.0#follower#upgradedClusterTest' -Dtests.class="org.elasticsearch.upgrades.CcrRollingUpgradeIT" -Dtests.method="testCannotFollowLeaderInUpgradedCluster" -Dtests.seed=27E3EAD1DEC83E86 -Dtests.bwc=true -Dtests.locale=sl-SI -Dtests.timezone=America/Caracas -Druntime.java=21
```

**Applicable branches:**
main

**Reproduces locally?:**
Yes

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.upgrades.CcrRollingUpgradeIT&tests.test=testCannotFollowLeaderInUpgradedCluster
**Failure excerpt:**
```
junit.framework.AssertionFailedError: Expected exception ResponseException but no exception was thrown

  at __randomizedtesting.SeedInfo.seed([27E3EAD1DEC83E86:A9BC1A5D74E1259D]:0)
  at org.apache.lucene.tests.util.LuceneTestCase.expectThrows(LuceneTestCase.java:2864)
  at org.apache.lucene.tests.util.LuceneTestCase.expectThrows(LuceneTestCase.java:2850)
  at org.elasticsearch.upgrades.CcrRollingUpgradeIT.testCannotFollowLeaderInUpgradedCluster(CcrRollingUpgradeIT.java:223)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
  at java.lang.reflect.Method.invoke(Method.java:580)
  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:1583)

```
x-pack/qa/rolling-upgrade-multi-cluster/src/test/java/org/elasticsearch/upgrades/CcrRollingUpgradeIT.java
""", leaderCluster, leaderIndex));
        assertOK(client.performRequest(request));
    }
    private static void followIndexIgnoringBadRequests(RestClient client, String leaderCluster, String leaderIndex, String followIndex)
        throws Exception {
        assertBusy(() -> {
            try {
                followIndex(client, leaderCluster, leaderIndex, followIndex);
            } catch (ResponseException e) {
                if (e.getResponse().getStatusLine().getStatusCode() == RestStatus.BAD_REQUEST.getStatus()) {
                    
                    
                    
                    throw new AssertionError(
                        "Receive bad request response after trying to follow index [" + leaderIndex + "], retrying",
                        e
                    );
                }
                throw e;
            }
        }, 30L, TimeUnit.SECONDS);
    }
    private static void putAutoFollowPattern(RestClient client, String name, String remoteCluster, String pattern) throws IOException {
        Request request = new Request("PUT", "/_ccr/auto_follow/" + name);
        request.setJsonEntity(Strings.format("""
            {
              "leader_index_patterns": [ "%s" ],
              "remote_cluster": "%s",
              "follow_index_pattern": "copy-{{leader_index}}",
              "read_poll_timeout": "10ms"