chore!: remove slack and deploy actions

With the migration to ArgoCD for deployments, the deploy action is no longer needed. The slack action was only a minimal wrapper around the official Slack GitHub Action, so users should use that directly instead.

Also removes the files filter from .pre-commit-config.yaml that was only needed for these removed actions.

BREAKING CHANGE: The `slack` and `deploy` actions are no longer available in this repository.

Author: grahamalama

.pre-commit-config.yaml

@@ -3,5 +3,3 @@ repos:
     rev: v0.7.0
     hooks:
       - id: action-readme
-        # TODO: After the `slack` and `deploy` actions are removed, remove this `files` input
-        files: "^(docker-build|docker-push)/"