Spell out duplicate hook locations.

props DrewAPicture.
fixes #25658.

Built from https://develop.svn.wordpress.org/trunk@25868


git-svn-id: http://core.svn.wordpress.org/trunk@25868 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/revision.php

@@ -70,7 +70,7 @@ function wp_get_revision_ui_diff( $post, $compare_from, $compare_to ) {
 		 */
 		$content_from = $compare_from ? apply_filters( "_wp_post_revision_field_$field", $compare_from->$field, $field, $compare_from, 'from' ) : '';
 
-		//duplicate_hook
+		/** This filter is documented in wp-admin/includes/revision.php */
 		$content_to = apply_filters( "_wp_post_revision_field_$field", $compare_to->$field, $field, $compare_to, 'to' );
 
 		$diff = wp_text_diff( $content_from, $content_to, array( 'show_split_view' => true ) );