dirstate: remove obsolete comment from setbranch

This comment should have been removed in b74361cf7c0a, when the call
to scmutil.checknewlabel was removed.

mercurial/dirstate.py

@@ -260,7 +260,6 b' class dirstate(object):'
         return copies
 
     def setbranch(self, branch):
-        # no repo object here, just check for reserved names
         self._branch = encoding.fromlocal(branch)
         f = self._opener('branch', 'w', atomictemp=True)
         try: