Bump docker/login-action from 1.8.0 to 2.0.0 (#6118)

Bumps [docker/login-action](https://github.com/docker/login-action) from 1.8.0 to 2.0.0.
- [Release notes](https://github.com/docker/login-action/releases)
- [Commits](https://github.com/docker/login-action/compare/v1.8.0...v2.0.0)

---
updated-dependencies:
- dependency-name: docker/login-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/boulder-ci.yml

@@ -76,7 +76,7 @@ jobs:
       - name: Docker Login
         # You may pin to the exact commit or the version.
         # uses: docker/login-action@f3364599c6aa293cdc2b8391b1b56d0c30e45c8a
-        uses: docker/login-action@v1.8.0
+        uses: docker/login-action@v2.0.0
         with:
           # Username used to log against the Docker registry
           username: ${{ secrets.DOCKER_USERNAME}}