path-suboption: use str for "pushrev" suboptions

That second argument refer to an attribute and do not needs to be bytes.

mercurial/utils/urlutil.py

@@ -720,7 +720,7 b' def pushurlpathoption(ui, path, value):'
     return bytes(u)
 
 
-@pathsuboption(b'pushrev', b'pushrev')
+@pathsuboption(b'pushrev', 'pushrev')
 def pushrevpathoption(ui, path, value):
     return value