[Tests] Fix De-/serialization tests of HighlightBuilder (#69259)

Assign a value different that the original when testing
mutation of the builder.

Follows: #67325

Author: matriv

server/src/test/java/org/elasticsearch/search/fetch/subphase/highlight/HighlightBuilderTests.java

@@ -681,7 +681,9 @@ private static void mutateCommonOptions(AbstractHighlighterBuilder highlightBuil
                 highlightBuilder.requireFieldMatch(toggleOrSet(highlightBuilder.requireFieldMatch()));
                 break;
             case 17:
-                highlightBuilder.maxAnalyzedOffset(randomIntBetween(1, 100));
+                highlightBuilder.maxAnalyzedOffset(
+                    randomValueOtherThan(highlightBuilder.maxAnalyzedOffset(), () -> randomIntBetween(1, 100))
+                );
                 break;
         }
     }