GitHub Apps: Replace grafanabot token with grafana-delivery-bot GitHub App (#70242)

* Update bump-version.yml

* Fix secret

* [REVERTME] Remove check

* Test without grafana-delivery-bot prefix

* Check if token exists

* Cleanup bump-version

* Update gh actions to use app key

.github/workflows/remove-milestone.yml

@@ -26,11 +26,17 @@ jobs:
           ref: main
       - name: Install Actions
         run: npm install --production --prefix ./actions
+      - name: "Generate token"
+          id: generate_token
+          uses: tibdex/github-app-token@b62528385c34dbc9f38e5f4225ac829252d1ea92
+          with:
+            app_id: ${{ secrets.GRAFANA_DELIVERY_BOT_APP_ID }}
+            private_key: ${{ secrets.GRAFANA_DELIVERY_BOT_APP_PEM }}
       - name: Remove milestone from open issues (manually invoked)
         if: ${{ github.event.inputs.version != '' }}
         uses: ./actions/remove-milestone
         with:
-          token: ${{ secrets.GH_BOT_ACCESS_TOKEN }}
+          token: ${{ steps.generate_token.outputs.token }}
       - name: Remove milestone from open issues (workflow invoked)
         if: ${{ inputs.version_call != '' }}
         uses: ./actions/remove-milestone