fix: leave on manual delete-packages.yml

leave it on manual control until the bug with multiarch is fixed.

https://github.com/dataaxiom/ghcr-cleanup-action/issues/35

.github/workflows/delete-packages.yml

@@ -1,13 +1,6 @@
 name: Delete untagged packages
 
-on:
-  workflow_run:
-    workflows:
-      - build-check
-      - Create and publish a Docker image
-      - format-check
-    types:
-      - completed
+on: workflow_dispatch
 
 jobs:
   delete-untagged-packages: