Fixed typo in comment (#51745)

Comment said the supporter highlighter type was fvj, there's no such highlighter. It is supposed to say fvh for fast vector highlighting.

Author: NoorKhan

server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/AbstractHighlighterBuilder.java

@@ -277,7 +277,7 @@ public Integer numOfFragments() {
 
     /**
      * Set type of highlighter to use. Out of the box supported types
-     * are {@code unified}, {@code plain} and {@code fvj}.
+     * are {@code unified}, {@code plain} and {@code fvh}.
      * Defaults to {@code unified}.
      * Details of the different highlighter types are covered in the reference guide.
      */