bundle2: don't check for whether we can do stream clones

At the moment this isn't used and all stream clones use the legacy protocol.

In an upcoming diff, canperformstreamclone will print out a message if a stream
clone was requested but couldn't happen for some reason. Removing this call
ensures the message isn't printed twice.

mercurial/exchange.py

@@ -1330,7 +1330,9 b' def _pullbundle2(pullop):'
     For now, the only supported data are changegroup."""
     kwargs = {'bundlecaps': caps20to10(pullop.repo)}
 
-    streaming, streamreqs = streamclone.canperformstreamclone(pullop)
+    # At the moment we don't do stream clones over bundle2. If that is
+    # implemented then here's where the check for that will go.
+    streaming = False
 
     # pulling changegroup
     pullop.stepsdone.add('changegroup')