chore(tools): remove merge-conflict action

.github/workflows/label_merge_conflicts.yml

@@ -1,13 +0,0 @@
-name: 'Check for merge conflicts'
-on:
-  schedule:
-    # run this Action every 12 hours
-    - cron:  '0 */12 * * *'
-jobs:
-  triage:
-    runs-on: ubuntu-18.04
-    steps:
-      - uses: mschilde/auto-label-merge-conflicts@master
-        with:
-          CONFLICT_LABEL_NAME: 'status: merge conflict'
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}