ci(automerge): remove action

This action was originally added on my repo so I could easily just apply
a label "automerge" on PRs that I wanted to merge automatically after
all the required tests passed. It's probably less useful here when
working with PRs from forks, since it reports failures on them.

.github/workflows/automerge.yml

@@ -1,26 +0,0 @@
-name: automerge
-on:
-  pull_request:
-    types:
-      - labeled
-      - synchronize
-      - opened
-      - edited
-      - ready_for_review
-      - reopened
-      - unlocked
-  check_suite:
-    types:
-      - completed
-  # status: {}
-jobs:
-  automerge:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Auto merge
-        uses: pascalgn/automerge-action@v0.12.0
-        env:
-          GITHUB_TOKEN: "${{ secrets.PAT }}"
-          MERGE_REMOVE_LABELS: "automerge"
-          # Using an unused label here to disable updating because using autoupdate action instead
-          UPDATE_LABELS: "disabled"