Remove workaround for requests < 2.0 on python 3

- this workaround caused systems with ndg-httpsclient installed to
  error out when requests is used
- requests versions 0.14.2 to 1.2.3 do not work due to unrelated issues
  and hence no point carrying this workaround
- requests version 0.14.1 and earlier works without this workaround

bugzilla/base.py

@@ -256,10 +256,6 @@ def request(self, host, handler, request_body, verbose=0):
         # xmlrpclib fails to escape \r
         request_body = request_body.replace(b'\r', b'
')
 
-        # Needed for python-requests < 2.0 with python3, otherwise we get
-        # Content-Type error later for the POST request
-        request_body = request_body.decode('utf-8')
-
         return self._request_helper(url, request_body)