phabricator: use True primitive instead of b'true' for phabupdate actions

Something I'd missed in the creatediff port.  This didn't matter before with
the old PHP form style wireformat, but breaks with the new arcanist format.

Differential Revision: https://phab.mercurial-scm.org/D7152

hgext/phabricator.py

@@ -1613,7 +1613,7 b' def phabupdate(ui, repo, spec, **opts):'
 
     actions = []
     for f in flags:
-        actions.append({b'type': f, b'value': b'true'})
+        actions.append({b'type': f, b'value': True})
 
     drevs = querydrev(repo, spec)
     for i, drev in enumerate(drevs):