subrepo: drop the 'ui' parameter to forget()

This no longer needs to be explicitly passed because the subrepo object tracks
the 'ui' reference since fcbc66b5da6a.  See the change to 'archive' for details
about the differences between the output level in the root repo and subrepo 'ui'
object.

The only use for 'ui' in forget is to emit status and warning messages, and to
check the verbose flag prior to printing files to be forgotten.  The bad()
method on the matcher still uses the root repo's ui, because narrowing the
matcher doesn't change the ui object.

The local repo's ui was already being used to print a warning message in
wctx.forget() and for 'ui.slash' when walking dirstate in the repo.status()
call.

mercurial/cmdutil.py

@@ -2028,7 +2028,7 b' def forget(ui, repo, match, prefix, expl'
         sub = wctx.sub(subpath)
         try:
             submatch = matchmod.narrowmatcher(subpath, match)
-            subbad, subforgot = sub.forget(ui, submatch, prefix)
+            subbad, subforgot = sub.forget(submatch, prefix)
             bad.extend([subpath + '/' + f for f in subbad])
             forgot.extend([subpath + '/' + f for f in subforgot])
         except error.LookupError:

mercurial/subrepo.py

@@ -496,7 +496,7 b' class abstractsubrepo(object):'
         '''
         pass
 
-    def forget(self, ui, match, prefix):
+    def forget(self, match, prefix):
         return ([], [])
 
     def removefiles(self, ui, matcher, prefix, after, force, subrepos):
@@ -850,8 +850,8 b' class hgsubrepo(abstractsubrepo):'
         return ctx.walk(match)
 
     @annotatesubrepoerror
-    def forget(self, ui, match, prefix):
-        return cmdutil.forget(ui, self._repo, match,
+    def forget(self, match, prefix):
+        return cmdutil.forget(self.ui, self._repo, match,
                               os.path.join(prefix, self._path), True)
 
     @annotatesubrepoerror