Merge BlockstreamResearch/secp256k1-zkp#349: sync-upstream: Pass token via checkout for git push operations

c9a623c362 sync-upstream: Pass token via checkout for git push operations (DarkWindman)

Pull request description:

  Pass token via checkout step for git operations.

  `git push` now uses the token from `actions/checkout`, not `GH_TOKEN` env var.

  Fixes authentication error when pushing workflow file changes.

ACKs for top commit:
  real-or-random:
    ACK c9a623c362

Tree-SHA512: a1ff1068d421f2bc390c589a4292d4d15788afcb9c42444af7bacf67103a761f2f90532dbb852081008632cf7bb1c6b99fe145178850c29d16470483fa221d1b

.github/workflows/sync.yml

@@ -23,6 +23,7 @@ jobs:
         uses: actions/checkout@v6
         with:
           fetch-depth: 0
+          token: ${{ secrets.SYNC_PAT }}
 
       - name: Configure Git
         run: |
@@ -65,8 +66,6 @@ jobs:
       - name: Generate PR metadata
         id: branch_pr_metadata
         if: steps.check_commits.outputs.skip == 'false'
-        env:
-          GH_TOKEN: ${{ secrets.SYNC_PAT }}
         run: |
           # Call the sync script to generate PR title and body
           ./contrib/sync-upstream.sh -b ${{ env.ORIGIN_BRANCH }} "$SYNC_BRANCH"
@@ -74,8 +73,6 @@ jobs:
       - name: Push a sync branch
         id: push_branch
         if: steps.check_commits.outputs.skip == 'false'
-        env:
-          GH_TOKEN: ${{ secrets.SYNC_PAT }}
         run: |
           echo "Creating sync branch: $SYNC_BRANCH"
           git checkout upstream/${{ env.UPSTREAM_BRANCH }}