ci: Remove "Add to docs project" workflow (#14417)

Co-authored-by: Christian Haudum <christian.haudum@gmail.com>
Co-authored-by: J Stickler <julie.stickler@grafana.com>

.github/workflows/add-to-docs-project.yml

@@ -1,15 +0,0 @@
-name: Add to docs project
-on:
-  issues:
-    types: [labeled]
-  pull_request:
-    types: [labeled]
-jobs:
-  main:
-    if: ${{ github.event.label.name == 'type/docs' }}
-    permissions:
-      contents: read
-      id-token: write
-    runs-on: ubuntu-latest
-    steps:
-      - uses: grafana/writers-toolkit/add-to-docs-project@add-to-docs-project/v1