### Description

The [bootstrap checks docs for 8.1](https://github.com/elastic/elasticsearch/blob/8.1/docs/reference/setup/bootstrap-checks.asciidoc#system-call-filter-check) still have a [section for disabling system call filters](https://www.elastic.co/guide/en/elasticsearch/reference/8.1/_system_call_filter_check.html) even though that setting was removed in 8.0 (#72848) and its removal is [listed in the breaking changes](https://www.elastic.co/guide/en/elastic-stack/8.0/elasticsearch-breaking-changes.html)


server/src/test/java/org/elasticsearch/bootstrap/BootstrapChecksTests.java
if (randomBoolean()) {
            context = createTestContext(Settings.builder().put("bootstrap.system_call_filter", true).build(), null);
        } else {
            context = emptyContext;
        }
        final BootstrapChecks.SystemCallFilterCheck systemCallFilterEnabledCheck = new BootstrapChecks.SystemCallFilterCheck() {
            @Override
            boolean isSystemCallFilterInstalled() {
                return isSystemCallFilterInstalled.get();
            }
        };
        final NodeValidationException e = expectThrows(
            NodeValidationException.class,
            () -> BootstrapChecks.check(context, true, Collections.singletonList(systemCallFilterEnabledCheck))
        );
        assertThat(e.getMessage(), containsString("system call filters failed to install; check the logs and fix your configuration"));
        isSystemCallFilterInstalled.set(true);
        BootstrapChecks.check(context, true, Collections.singletonList(systemCallFilterEnabledCheck));
    }
    public void testMightForkCheck() throws NodeValidationException {
        final AtomicBoolean isSystemCallFilterInstalled = new AtomicBoolean();
        final AtomicBoolean mightFork = new AtomicBoolean();
        final BootstrapChecks.MightForkCheck check = new BootstrapChecks.MightForkCheck() {
            @Override
            boolean isSystemCallFilterInstalled() {
                return isSystemCallFilterInstalled.get();
            }
            @Override
            boolean mightFork() {
                return mightFork.get();