Remove WP_Theme::is_child_theme() in favor of WP_Theme::parent(). see #20546.

git-svn-id: https://develop.svn.wordpress.org/trunk@20589 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/class-wp-theme.php

@@ -744,18 +744,6 @@ final class WP_Theme implements ArrayAccess {
 		return $this->template;
 	}
 
-	/**
-	 * Whether a theme is a child theme.
-	 *
-	 * @since 3.4.0
-	 * @access public
-	 *
-	 * @return bool True if a theme is a child theme, false otherwise.
-	 */
-	public function is_child_theme() {
-		return $this->template !== $this->stylesheet;
-	}
-
 	/**
 	 * Returns the absolute path to the directory of a theme's "stylesheet" files.
 	 *