Bump google-github-actions/auth from 2.1.5 to 2.1.6

Bumps [google-github-actions/auth](https://github.com/google-github-actions/auth) from 2.1.5 to 2.1.6.
- [Release notes](https://github.com/google-github-actions/auth/releases)
- [Changelog](https://github.com/google-github-actions/auth/blob/main/CHANGELOG.md)
- [Commits](google-github-actions/auth@v2.1.5...v2.1.6)

---
updated-dependencies:
- dependency-name: google-github-actions/auth
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

.github/workflows/functional_test_v2.yaml

@@ -228,7 +228,7 @@ jobs:
             ~/go/bin
             ~/go/pkg/mod
           key: go-cache-${{ runner.os }}-${{ hashFiles('**/go.sum') }}
-      - uses: 'google-github-actions/[email protected].5'
+      - uses: 'google-github-actions/[email protected].6'
         with:
           project_id: ${{ secrets.GKE_PROJECT }}
           credentials_json: ${{ secrets.GKE_SA_KEY }}
@@ -291,7 +291,7 @@ jobs:
             ~/go/bin
             ~/go/pkg/mod
           key: go-cache-${{ runner.os }}-${{ hashFiles('**/go.sum') }}
-      - uses: 'google-github-actions/[email protected].5'
+      - uses: 'google-github-actions/[email protected].6'
         with:
           project_id: ${{ secrets.GKE_PROJECT }}
           credentials_json: ${{ secrets.GKE_SA_KEY }}