[test_age_restriction] remove misbehaving test

We now test for the age_limit being set right in test_download, so we don't need more than two tests for the actual age limit handling.

test/test_age_restriction.py

@@ -45,11 +45,6 @@ def test_youporn(self):
             'http://www.youporn.com/watch/505835/sex-ed-is-it-safe-to-masturbate-daily/',
             '505835.mp4', 2, old_age=25)
 
-    def test_pornotube(self):
-        self._assert_restricted(
-            'http://pornotube.com/c/173/m/1689755/Marilyn-Monroe-Bathing',
-            '1689755.flv', 13)
-
 
 if __name__ == '__main__':
     unittest.main()