Add a proper description comment for the WP_Image_Editor_GD->$image property.

See [30180]. See #30224.


git-svn-id: https://develop.svn.wordpress.org/trunk@32554 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-image-editor-gd.php

@@ -16,9 +16,12 @@
  */
 class WP_Image_Editor_GD extends WP_Image_Editor {
 	/**
+	 * GD Resource.
+	 *
+	 * @access protected
 	 * @var resource
 	 */
-	protected $image; // GD Resource
+	protected $image;
 
 	public function __destruct() {
 		if ( $this->image ) {