obsolete: use the `version` argument in encodemarkers

Recent scientific studies show that assigning a variable have no effect on
a unrelated constant. We therefore use the variable where we intended to in the
first place.

mercurial/obsolete.py

@@ -227,7 +227,7 b' def encodemarkers(markers, addheader=Fal'
     # markers exchange.
     encodeone = formats[version][1]
     if addheader:
-        yield _pack('>B', _fm0version)
+        yield _pack('>B', version)
     for marker in markers:
         yield encodeone(marker)