Update date format warning regex with more text specifiers (#113001) (#113010)

Author: thecoop

server/src/main/java/org/elasticsearch/common/time/DateUtils.java

@@ -389,8 +389,9 @@ public static ZonedDateTime nowWithMillisResolution(Clock clock) {
     }
 
     // check for all textual fields, and localized zone offset
+    // the weird thing with Z is to ONLY match 4 in a row, with no Z before or after (but those groups can also be empty)
     private static final Predicate<String> CONTAINS_CHANGING_TEXT_SPECIFIERS = System.getProperty("java.locale.providers", "")
-        .contains("COMPAT") ? Pattern.compile("[EcGaO]|MMM|LLL|eee|ccc|QQQ|ZZZZ").asPredicate() : Predicates.never();
+        .contains("COMPAT") ? Pattern.compile("[BEGOavz]|LLL|MMM|QQQ|ccc|eee|(?<!Z)Z{4}(?!Z)").asPredicate() : Predicates.never();
 
     @UpdateForV9    // this can be removed, we will only use CLDR on v9
     static void checkTextualDateFormats(String format) {