Code Modernization: Fix reserved keyword and parameter name mismatches for parent/child classes in Walker::end_el().

In the parent class, renames the parameter `$object` to `$data_object`.
Why? `object` is a PHP reserved keyword. The parameter name is selected for consistency with `Walker::start_el()`.

In each child class: renames the parameter to match the parent's method signature.
Why? PHP 8 introduces the ability to pass named arguments to function/method calls. This means the child and parent method signatures (i.e. parameter names) need to match.

Changes for readability:

- `@since` clearly specifies the original parameter name and its new name as well as why the change happened.

Follow-up to [7737], [8900], [8970], [14248], [16100], [25642], [25644], [37051], [37056].

Props jrf, hellofromTonya, sergeybiryukov, azaozz, desrosj, johnbillion.
See #51553.

git-svn-id: https://develop.svn.wordpress.org/trunk@51780 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-walker.php

@@ -100,14 +100,15 @@ class Walker {
 	 * The $args parameter holds additional values that may be used with the child class methods.
 	 *
 	 * @since 2.1.0
+	 * @since 5.9.0 Renamed `$object` (a PHP reserved keyword) to `$data_object` for PHP 8 named parameter support.
 	 * @abstract
 	 *
-	 * @param string $output Used to append additional content (passed by reference).
-	 * @param object $object The data object.
-	 * @param int    $depth  Depth of the item.
-	 * @param array  $args   An array of additional arguments.
+	 * @param string $output      Used to append additional content (passed by reference).
+	 * @param object $data_object The data object.
+	 * @param int    $depth       Depth of the item.
+	 * @param array  $args        An array of additional arguments.
 	 */
-	public function end_el( &$output, $object, $depth = 0, $args = array() ) {}
+	public function end_el( &$output, $data_object, $depth = 0, $args = array() ) {}
 
 	/**
 	 * Traverse elements to create list from elements.