changegroup: remove unused variable caught by pyflakes

mercurial/changegroup.py

@@ -358,7 +358,7 b' class bundle10(object):'
 
         def linknodes(filerevlog, fname):
             if fastpathlinkrev:
-                ln, llr = filerevlog.node, filerevlog.linkrev
+                llr = filerevlog.linkrev
                 def genfilenodes():
                     for r in filerevlog:
                         linkrev = llr(r)