MDL-66335 behat: Avoid double processing the page type

resolve_page_instance_helper() already processes the type, returning
the correct context that should be processing the navigation URL.

With that extra call to parse_page_name() the 2nd call always returns
"core", ultimately leading to tons of behat failures because "core" is
not aware of those (plugin, quiz for now) pages typology.

lib/tests/behat/behat_navigation.php

@@ -646,7 +646,6 @@ class behat_navigation extends behat_base {
      * @throws Exception if the specified page cannot be determined.
      */
     public function i_am_on_page_instance(string $identifier, string $type) {
-        list($component, $type) = $this->parse_page_name($type);
         $this->getSession()->visit($this->locate_path(
                 $this->resolve_page_instance_helper($identifier, $type)->out_as_local_url()));
     }