Bump docker/build-push-action from 6.3.0 to 6.4.0 (#325)

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.3.0 to 6.4.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@1a16264...a254f8c)

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

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

.github/workflows/ci.yml

@@ -68,7 +68,7 @@ jobs:
         uses: docker/setup-buildx-action@4fd812986e6c8c2a69e18311145f9371337f27d4 # v3.4.0
 
       - name: Build Plus Docker Image
-        uses: docker/build-push-action@1a162644f9a7e87d8f4b053101d1d9a712edc18c # v6.3.0
+        uses: docker/build-push-action@a254f8ca60a858f3136a2f1f23a60969f2c402dd # v6.4.0
         with:
           file: docker/Dockerfile
           tags: nginx-plus