Bump actions/setup-go from 5 to 6 in the github-actions group

Bumps the github-actions group with 1 update: [actions/setup-go](https://github.com/actions/setup-go).


Updates `actions/setup-go` from 5 to 6
- [Release notes](https://github.com/actions/setup-go/releases)
- [Commits](actions/setup-go@v5...v6)

---
updated-dependencies:
- dependency-name: actions/setup-go
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/upstream-refs.yml

@@ -25,7 +25,7 @@ jobs:
           repository: stolostron/governance-policy-framework
           ref: ${{ github.event.pull_request.base.ref }}
       - name: Set up Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version-file: governance-policy-framework/go.mod
           cache-dependency-path: governance-policy-framework/go.sum