bundle2: add debug info about the number of stream params

Seems like the %i was never substituted.

mercurial/bundle2.py

@@ -349,7 +349,7 b' def processbundle(repo, unbundler, trans'
     if repo.ui.debugflag:
         msg = ['bundle2-input-bundle:']
         if unbundler.params:
-            msg.append(' %i params')
+            msg.append(' %i params' % len(unbundler.params))
         if op.gettransaction is None or op.gettransaction is _notransaction:
             msg.append(' no-transaction')
         else: