Bump docker/build-push-action from 6.7.0 to 6.9.0 (#258)

* Bump docker/build-push-action from 6.7.0 to 6.9.0

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.7.0 to 6.9.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@5cd11c3...4f58ea7)

---
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>

* format: change from legacy keyword format

https://docs.docker.com/reference/build-checks/legacy-key-value-format/

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Christian Willner <34183939+vaeng@users.noreply.github.com>

.github/workflows/test.yml

@@ -22,7 +22,7 @@ jobs:
           install: true
 
       - name: Build Docker image and store in cache
-        uses: docker/build-push-action@5cd11c3a4ced054e52742c5fd54dca954e0edd85
+        uses: docker/build-push-action@4f58ea79222b3b9dc2c8bbdd6debcef730109a75
         with:
           context: .
           push: false

Dockerfile

@@ -38,7 +38,7 @@ FROM mcr.microsoft.com/dotnet/sdk:8.0.201-alpine3.19-amd64 AS runtime
 WORKDIR /opt/test-runner
 
 # Enable rolling forward the .NET SDK used to be backwards-compatible
-ENV DOTNET_ROLL_FORWARD Major
+ENV DOTNET_ROLL_FORWARD=Major
 
 COPY --from=build /root/.nuget/packages/ /root/.nuget/packages/
 COPY --from=build /opt/test-runner/ .