deposit: remove old user email when present

* the `_cds.current_user_mail` has been removed, however it might still
  be present in some previous records' revisions. This makes the
  publishing of editing videos fail. When the `_cds.current_user_mail`
  is found while publishing, it is ignored.

cds/modules/invenio_deposit/api.py

@@ -188,6 +188,8 @@ def merge_with_published(self):
         args = [lca.dumps(), first.dumps(), self.dumps()]
         for arg in args:
             del arg["$schema"], arg["_deposit"]
+            # pop optional removed key `current_user_mail` when present
+            arg.get("_cds", {}).pop("current_user_mail", None)
         args.append({})
         m = Merger(*args)
         try: