httppeer: remove redundant code to fetch capabilities _fetchcaps() is called by httppeer.instance(), which is the only instantiator of httppeer. Since _fetchcaps() always sets self._caps and since 197d10e157ce removed the fallback for cases where the remote doesn't support capabilities, we can remove some dead code from httppeer.capabilities(). Differential Revision: https://phab.mercurial-scm.org/D2215