forget: don't report rejected files as forgotten as well

It seems like a mistake to report a file as forgotten and rejected.  The
forgotten list doesn't seem to be used by anything in core, so no test changes.

mercurial/cmdutil.py

@@ -2057,7 +2057,7 b' def forget(ui, repo, match, prefix, expl'
 
     rejected = wctx.forget(forget, prefix)
     bad.extend(f for f in rejected if f in match.files())
-    forgot.extend(forget)
+    forgot.extend(f for f in forget if f not in rejected)
     return bad, forgot
 
 def remove(ui, repo, m, prefix, after, force, subrepos):