docs(hooks): update process_text_diff_html xrefs

Update 2 cross-references for process_text_diff_html
from non-existent `wp-diff.php` to the actual file
`class-wp-text-diff-renderer-table.php`.

Related to https://core.trac.wordpress.org/ticket/64224

Author: apermo

src/wp-includes/class-wp-text-diff-renderer-table.php

@@ -235,7 +235,7 @@ public function _deleted( $lines, $encode = true ) {
 			if ( $encode ) {
 				$processed_line = htmlspecialchars( $line );
 
-				/** This filter is documented in wp-includes/wp-diff.php */
+				/** This filter is documented in wp-includes/class-wp-text-diff-renderer-table.php */
 				$line = apply_filters( 'process_text_diff_html', $processed_line, $line, 'deleted' );
 			}
 			if ( $this->_show_split_view ) {
@@ -260,7 +260,7 @@ public function _context( $lines, $encode = true ) {
 			if ( $encode ) {
 				$processed_line = htmlspecialchars( $line );
 
-				/** This filter is documented in wp-includes/wp-diff.php */
+				/** This filter is documented in wp-includes/class-wp-text-diff-renderer-table.php */
 				$line = apply_filters( 'process_text_diff_html', $processed_line, $line, 'unchanged' );
 			}
 			if ( $this->_show_split_view ) {