debugcommands: use openstorage() in debugdata (BC)

Nothing we're doing here requires a revlog. So use openstorage().

.. bc::

   `hg debugdata` no longer accepts the path to a revlog file.

Differential Revision: https://phab.mercurial-scm.org/D4357

mercurial/debugcommands.py

@@ -556,7 +556,7 b' def debugdata(ui, repo, file_, rev=None,'
         file_, rev = None, file_
     elif rev is None:
         raise error.CommandError('debugdata', _('invalid arguments'))
-    r = cmdutil.openrevlog(repo, 'debugdata', file_, opts)
+    r = cmdutil.openstorage(repo, 'debugdata', file_, opts)
     try:
         ui.write(r.revision(r.lookup(rev), raw=True))
     except KeyError: