wireprotoframing: remove Python 2 support code

Differential Revision: https://phab.mercurial-scm.org/D12303

mercurial/wireprotoframing.py

@@ -761,11 +761,6 b' class zlibdecoder(object):'
         self._decompressor = zlib.decompressobj()
 
     def decode(self, data):
-        # Python 2's zlib module doesn't use the buffer protocol and can't
-        # handle all bytes-like types.
-        if not pycompat.ispy3 and isinstance(data, bytearray):
-            data = bytes(data)
-
         return self._decompressor.decompress(data)