Improve some docs for @param. Remove an unneeded $wpdb global import.

See #30799.


git-svn-id: https://develop.svn.wordpress.org/trunk@30979 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -194,6 +194,7 @@ abstract class WP_Image_Editor {
 	 *
 	 * @param int $width
 	 * @param int $height
+	 * @return true
 	 */
 	protected function update_size( $width = null, $height = null ) {
 		$this->size = array(
@@ -388,7 +389,7 @@ abstract class WP_Image_Editor {
 	 * @since 3.5.0
 	 * @access public
 	 *
-	 * @return string suffix
+	 * @return false|string suffix
 	 */
 	public function get_suffix() {
 		if ( ! $this->get_size() )