Remove deprecated Pico::getBaseThemeUrl()

Use Pico::getConfig('themes_url') instead.

lib/Pico.php

@@ -2389,20 +2389,6 @@ class Pico
         return str_replace(array_keys($variables), $variables, $url);
     }
 
-    /**
-     * Returns the URL of the themes folder of this Pico instance
-     *
-     * @see Pico::getUrlFromPath()
-     *
-     * @deprecated 2.1.0
-     *
-     * @return string
-     */
-    public function getBaseThemeUrl()
-    {
-        return $this->getConfig('themes_url');
-    }
-
     /**
      * Returns the URL of a given absolute path within this Pico instance
      *