github: Configure a single Github actions token

.github/workflows/labeler.yml

@@ -13,5 +13,5 @@ jobs:
     steps:
       - uses: actions/labeler@v4
         with:
-          repo-token: "${{ secrets.GITHUB_TOKEN }}"
+          repo-token: "${{ secrets.GH_TOKEN }}"
           configuration-path: .github/labeler.yml

.github/workflows/stale.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Close stale pull requests
         uses: actions/stale@v6
         with:
-          repo-token: ${{ secrets.STALE_GH_TOKEN }}
+          repo-token: ${{ secrets.GH_TOKEN }}
           operations-per-run: 1000
           ascending: true
           stale-pr-message: 'This pull request has been marked as stale due to inactivity. It will be closed in 7 days if no further activity occurs.'