SECURITY: Fix Compile Error in ReservedRealmTests (#33166)

* This was broken by #32515 since the 5.x versions
were removed between PR creation and merge

Author: original-brownbear

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/esnative/ReservedRealmTests.java

@@ -456,7 +456,6 @@ private void verifyVersionPredicate(String principal, Predicate<Version> version
                 assertThat(versionPredicate.test(Version.V_6_3_0), is(true));
                 break;
             case APMSystemUser.NAME:
-                assertThat(versionPredicate.test(Version.V_5_6_9), is(false));
                 assertThat(versionPredicate.test(Version.V_6_4_0), is(false));
                 assertThat(versionPredicate.test(Version.V_6_5_0), is(true));
                 break;