narrow: stop using `drop` in the `updateworkingcopy`

Let us use the new API instead.

Differential Revision: https://phab.mercurial-scm.org/D11194

mercurial/narrowspec.py

@@ -343,7 +343,7 b' def updateworkingcopy(repo, assumeclean='
     for f in sorted(status.ignored):
         repo.ui.status(_(b'not deleting ignored file %s\n') % uipathfn(f))
     for f in clean + trackeddirty:
-        ds.drop(f)
+        ds.update_file(f, p1_tracked=False, wc_tracked=False)
 
     pctx = repo[b'.']