linkifiers: Remove outdated comment in tests.

After 34e39248fc, we do support
generic GitHub URLs. This test and the comment above
it were added in 043baa2af8.

zerver/tests/test_realm_filters.py

@@ -88,9 +88,6 @@ class RealmFilterTest(ZulipTestCase):
         self.assert_json_success(result)
         self.assertIsNotNone(re.match(data["pattern"], "!123"))
 
-        # This is something we'd like to support, but don't currently;
-        # this test is a reminder of something we should allow in the
-        # future.
         data["pattern"] = r"(?P<org>[a-zA-Z0-9_-]+)/(?P<repo>[a-zA-Z0-9_-]+)#(?P<id>[0-9]+)"
         data["url_format_string"] = "https://github.com/%(org)s/%(repo)s/issue/%(id)s"
         result = self.client_post("/json/realm/filters", info=data)