wireprotov2server: don't attempt to cast command name

I'm not sure why this was added. The command name should already
be bytes.

Differential Revision: https://phab.mercurial-scm.org/D5697

mercurial/wireprotov2server.py

@@ -745,7 +745,7 b' def makecommandcachekeyfn(command, local'
             # More granular cache key invalidation.
             b'localversion': localversion,
             # Cache keys are segmented by command.
-            b'command': pycompat.sysbytes(command),
+            b'command': command,
             # Throw in the media type and API version strings so changes
             # to exchange semantics invalid cache.
             b'mediatype': FRAMINGTYPE,