fix forbidden api violation by avoiding default-locale usage

Signed-off-by: Jackie <[email protected]>

Author: jackiehanyang

src/main/java/org/opensearch/ad/ml/InsightsGenerator.java

@@ -217,10 +217,7 @@ private static String generateParagraphText(
     ) {
         StringBuilder text = new StringBuilder();
 
-        DateTimeFormatter friendlyFormatter = DateTimeFormatter
-            .ofPattern("MMM d, yyyy HH:mm z")
-            .withLocale(Locale.ROOT)
-            .withZone(ZoneOffset.UTC);
+        DateTimeFormatter friendlyFormatter = DateTimeFormatter.ofPattern("MMM d, yyyy HH:mm z", Locale.ROOT).withZone(ZoneOffset.UTC);
         String startStr = friendlyFormatter.format(eventStart);
         String endStr = friendlyFormatter.format(eventEnd);