Fix inform_pull_request_urls in the default hook

The function requires 5 arguments, not 6.
Broken in 07b517e2fa1f40ea872cf60eb06b92ce2cd88e09

Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>

pagure/hooks/default.py

@@ -446,7 +446,6 @@ class DefaultRunner(BaseRunner):
                     project,
                     commits,
                     refname,
-                    default_branch,
                     username,
                 )
             )