Correct the usage of tokens in SRI update workflow

This used an outdated / no-longer-used token; let's see if I can use
the app instead (which is what it was intended to use anyway).

.github/workflows/regenerate-go-sri.yml

@@ -35,7 +35,7 @@ jobs:
           private_key: ${{ secrets.PR_FIXUP_APP_PRIVATE_KEY }}
       - uses: actions/checkout@v4
         with:
-          token: ${{secrets.REPO_CONTENT_UPDATE_TOKEN}}
+          token: ${{steps.generate_token.outputs.token}}
           fetch-depth: 0 # otherwise, you will failed to push refs to dest repo
       - uses: cachix/install-nix-action@v30
       - uses: DeterminateSystems/magic-nix-cache-action@v8