frontend: regenerate devel repository when multiple builds are deleted

Fix fedora-copr#3507

The issue was introduced in PR fedora-copr#3330. We previously did this on
the backend:

    devel = uses_devel_repo(self.front_url, ownername, projectname)

It looks like an unnecessary request, so I am sending the attribute
as a part of the action data.

frontend/coprs_frontend/coprs/logic/actions_logic.py

@@ -224,6 +224,7 @@ def send_delete_multiple_builds(cls, builds):
             # We can pick any random build because the assumption is, they are
             # all from the same project
             "storage": builds[0].copr.storage if builds else None,
+            "devel": builds[0].copr.devel_mode,
         }
 
         build_ids = []