mq: use `set_untracked` in `qrename`

This is the new shiny API.

Differential Revision: https://phab.mercurial-scm.org/D11021

hgext/mq.py

@@ -3640,7 +3640,7 b' def rename(ui, repo, patch, name=None, *'
         wctx = r[None]
         with r.wlock():
             if r.dirstate[patch] == b'a':
-                r.dirstate.drop(patch)
+                r.dirstate.set_untracked(patch)
                 r.dirstate.set_tracked(name)
             else:
                 wctx.copy(patch, name)