Bump actions/setup-go from 6 to 7

Bumps [actions/setup-go](https://github.com/actions/setup-go) from 6 to 7.
- [Release notes](https://github.com/actions/setup-go/releases)
- [Commits](actions/setup-go@v6...v7)

---
updated-dependencies:
- dependency-name: actions/setup-go
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Install Go
-      uses: actions/setup-go@v6
+      uses: actions/setup-go@v7
       with:
         go-version: "1.25" # ideally matches Heroku
     - name: Checkout code