debugcommands: mergestate version is an int, use %d on it

Differential Revision: https://phab.mercurial-scm.org/D2227

mercurial/debugcommands.py

@@ -1406,7 +1406,7 b' def debugmergestate(ui, repo, *args):'
             return h
 
     def printrecords(version):
-        ui.write(('* version %s records\n') % version)
+        ui.write(('* version %d records\n') % version)
         if version == 1:
             records = v1records
         else: