ci: use builtin GITEA_TOKEN

.gitea/workflows/submodule-bump.yaml

@@ -34,11 +34,10 @@ jobs:
         uses: actions/checkout@v4
         with:
           submodules: true
-          token: ${{ secrets.BOT_TOKEN }}
 
       - name: Bump ${{ matrix.name }} and open PR
         env:
-          TOKEN: ${{ secrets.BOT_TOKEN }}
+          TOKEN: ${{ secrets.GITEA_TOKEN }}
           API: ${{ github.api_url }}
           REPO: ${{ github.repository }}
           NAME: ${{ matrix.name }}