convert: fix argument mismatch at formatting the abort message

This patch fixes argument mismatch at formatting the abort message,
introduced by a204fd9b5ba9: the last '%s' doesn't have corresponded
argument.

This patch uses "unexpected size" in the abort message, to distinguish
the reason of failure from "unexpected type" failure checked in the
prior code path below:

        if info[1] != type:
            raise util.Abort(_('cannot read %r object at %s') % (type, rev))

hgext/convert/git.py

@@ -127,7 +127,8 b' class convert_git(converter_source):'
         size = int(info[2])
         data = self.catfilepipe[1].read(size)
         if len(data) < size:
-            raise util.Abort(_('cannot read %r object at %s: %s') % (type, rev))
+            raise util.Abort(_('cannot read %r object at %s: unexpected size')
+                             % (type, rev))
         # read the trailing newline
         self.catfilepipe[1].read(1)
         return data