wireproto: remove unnecessary exception trapping The `try..except error.Abort` was added in 8474be4412ca back in 2012. The intent was to ensure a failing pushkey hook didn't crash the server. Since that changeset, repo.pushkey() and the hooks mechanism is now much more robust about trapping errors itself. As such, we no longer need this try..except block. So it has been removed. Differential Revision: https://phab.mercurial-scm.org/D1996