6441827: Documentation mentions nonexistent NullReferenceException

Reviewed-by: iris

src/java.base/share/classes/java/io/ObjectOutputStream.java

@@ -585,7 +585,7 @@ protected void annotateProxyClass(Class<?> cl) throws IOException {
      * substituted or the original object.
      *
      * <p>Null can be returned as the object to be substituted, but may cause
-     * NullReferenceException in classes that contain references to the
+     * {@link NullPointerException} in classes that contain references to the
      * original object since they may be expecting an object instead of
      * null.
      *