Disable unsupported build opts in monthly workflow

- explicitly disable building packages
- explicitly disable generating release builds using podman
- configure workflow_displatch event to permit on-demand workflow runs
  for future troubleshooting purposes

.github/workflows/scheduled-monthly.yml

@@ -15,7 +15,15 @@ on:
  # * * * * *
  - cron: "30 4 1 * *"
 
+ # Allow triggering workflow manually
+ # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_dispatch
+ workflow_dispatch:
+
 jobs:
  monthly:
  name: Monthly Tasks
  uses: atc0005/shared-project-resources/.github/workflows/scheduled-monthly.yml@master
+ with:
+ build-packages: false
+ build-podman-release: false
+