typing: suppress a false error in mercurial/revlogutils/docket.py on py2

`ord()` wants bytes or str on py3, so I'm guessing it got confused by passing a
single byte instead of a one byte string.  But this seems to work on 2.7.18
anyway.

Differential Revision: https://phab.mercurial-scm.org/D10876

mercurial/revlogutils/docket.py

@@ -60,7 +60,9 b' if stable_docket_file:'
         if pycompat.ispy3:
             iter_seed = iter(seed)
         else:
+            # pytype: disable=wrong-arg-types
             iter_seed = (ord(c) for c in seed)
+            # pytype: enable=wrong-arg-types
         # some basic circular sum hashing on 64 bits
         int_seed = 0
         low_mask = int('1' * 35, 2)