PHP 8: fix fatal "argument must be passed by reference, value given"

This fixes the following unit test failures:
```
1) Tests_Admin_includesListTable::test_filter_button_should_be_shown_if_there_are_comments

get_comment(): Argument #1 ($comment) must be passed by reference, value given

2) Tests_Admin_includesListTable::test_filter_comment_status_dropdown_should_be_shown_if_there_are_comments

get_comment(): Argument #1 ($comment) must be passed by reference, value given

14) WP_Test_Block_Render::test_render_latest_comments_on_password_protected_post

get_comment(): Argument #1 ($comment) must be passed by reference, value given
```

src/wp-includes/class-wp-comment-query.php

@@ -481,7 +481,8 @@ public function get_comments() {
 		$_comments = apply_filters_ref_array( 'the_comments', array( $_comments, &$this ) );
 
 		// Convert to WP_Comment instances.
-		$comments = array_map( 'get_comment', $_comments );
+		array_walk( $_comments, 'get_comment' );
+		$comments = $_comments;
 
 		if ( $this->query_vars['hierarchical'] ) {
 			$comments = $this->fill_descendants( $comments );