Bump docker/build-push-action from 3.3.0 to 4.0.0 (#28)

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 3.3.0 to 4.0.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v3.3.0...v4.0.0)

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

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

.github/workflows/ci-build.yml

@@ -23,7 +23,7 @@ jobs:
         username: ${{ github.repository_owner }}
         password: ${{ secrets.GITHUB_TOKEN }}
     - name: Build and push Docker images
-      uses: docker/build-push-action@v3.3.0
+      uses: docker/build-push-action@v4.0.0
       with:
         tags: ghcr.io/beryju/saml-test-sp:latest
         push: ${{ github.ref == 'refs/heads/master' }}