Coding Standards: Remove unused variable in `wp-trackback.php`.

This was present in the initial import of b2 files, but appears to have never been used in WordPress core.

Follow-up to [3], [636], [637], [1616].

See #55647.
Built from https://develop.svn.wordpress.org/trunk@53720


git-svn-id: http://core.svn.wordpress.org/trunk@53279 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-53719';
+$wp_version = '6.1-alpha-53720';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

wp-trackback.php

@@ -42,9 +42,6 @@ function trackback_response( $error = 0, $error_message = '' ) {
 	}
 }
 
-// Trackback is done by a POST.
-$request_array = 'HTTP_POST_VARS';
-
 if ( ! isset( $_GET['tb_id'] ) || ! $_GET['tb_id'] ) {
 	$post_id = explode( '/', $_SERVER['REQUEST_URI'] );
 	$post_id = (int) $post_id[ count( $post_id ) - 1 ];