wireprotoserver: remove broken optimization for non-httplib client There was an experimental non-httplib client in core for several years. It was removed a week or so ago. We kept the optimization for this client in the server code. I'm not sure if that was intended or not. But it doesn't matter: the code was wrong. Because the code was accessing a WSGI environment dict, it needed to access the HTTP_X_HGHTTP2 key to actually read the HTTP header. So the code deleted by this commit wasn't actually doing anything meaningful. Doh. Differential Revision: https://phab.mercurial-scm.org/D2741