[ci] Remove polkadot-companion-labels GHA (#11774)

substrate/.github/workflows/polkadot-companion-labels.yml

-name: Check Polkadot Companion and Label
-
-on:
-  pull_request:
-    types: [opened, synchronize]
-  
-jobs:
-  check_status:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Monitor the status of the gitlab-check-companion-build job
-        uses: s3krit/await-status-action@v1.0.1
-        id: 'check-companion-status'
-        with:
-          authToken: ${{ secrets.GITHUB_TOKEN }}
-          ref: ${{ github.event.pull_request.head.sha }}
-          contexts: 'continuous-integration/gitlab-check-dependent-polkadot'
-          timeout: 1800
-          notPresentTimeout: 3600 # It can take quite a while before the job starts on Gitlab when the CI queue is large
-          failureStates: failure
-          interruptedStates: error # Error = job was probably cancelled. We don't want to label the PR in that case
-          pollInterval: 30
-      - name: Label success
-        uses: andymckay/labeler@master
-        if: steps.check-companion-status.outputs.result == 'success'
-        with:
-          remove-labels: 'A7-needspolkadotpr'
-      - name: Label failure
-        uses: andymckay/labeler@master
-        if: steps.check-companion-status.outputs.result == 'failure'
-        with:
-          add-labels: 'A7-needspolkadotpr'