casper: Remove phantom_page_loaded code.

We removed the phantom_page_loaded logic in
b13265d135
(July 2017).

Now we just say that the page is loaded
to the console, which can possibly help
us debug glitches where the tests are
executing too early.

frontend_tests/casper_lib/common.js

@@ -65,10 +65,7 @@ exports.initialize_casper = function () {
     });
 
     casper.on('load.finished', function () {
-        casper.evaluateOrDie(function () {
-            $(document).trigger($.Event('phantom_page_loaded'));
-            return true;
-        });
+        casper.test.info('page load finished');
     });
 
     // This function should always be enclosed within a then() otherwise