perf: properly process formatter option in perf::unbundle

Otherwise, the options are not understood.

contrib/perf.py

@@ -2666,6 +2666,8 b' def perf_unbundle(ui, repo, fname, **opt'
     from mercurial import exchange
     from mercurial import bundle2
 
+    opts = _byteskwargs(opts)
+
     with repo.lock():
         bundle = [None, None]
         orig_quiet = repo.ui.quiet