py3: use pycompat.sysargv in dispatch.run()

Another one to have a bytes result from sys.argv in Python 3.
This one is also a part of running `hg version` on Python 3.

mercurial/dispatch.py

@@ -36,6 +36,7 b' from . import ('
     hg,
     hook,
     profiling,
+    pycompat,
     revset,
     templatefilters,
     templatekw,
@@ -58,7 +59,7 b' class request(object):'
 
 def run():
     "run the command in sys.argv"
-    sys.exit((dispatch(request(sys.argv[1:])) or 0) & 255)
+    sys.exit((dispatch(request(pycompat.sysargv[1:])) or 0) & 255)
 
 def _getsimilar(symbols, value):
     sim = lambda x: difflib.SequenceMatcher(None, value, x).ratio()