wrapfunction: use sysstr instead of bytes as argument in "clonebundles"

This is as valid and simpler, it will help us to eventually get ride of
`safehasattr`.

hgext/clonebundles.py

@@ -349,7 +349,7 b' def capabilities(orig, repo, proto):'
 
 
 def extsetup(ui):
-    extensions.wrapfunction(wireprotov1server, b'_capabilities', capabilities)
+    extensions.wrapfunction(wireprotov1server, '_capabilities', capabilities)
 
 
 # logic for bundle auto-generation