build(deps): bump docker/build-push-action from 5 to 6

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 5 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v5...v6)

---
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]>

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
 
       - name: Build Docker image
         if: github.event_name != 'schedule'
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           tags: espressif/rust-std-training

.github/workflows/docker_image.yml

@@ -43,7 +43,7 @@ jobs:
 
       - name: Build Docker image
         if: github.event_name != 'schedule'
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           tags: espressif/rust-std-training
@@ -78,7 +78,7 @@ jobs:
           password: ${{ secrets.DOCKER_TOKEN }}
 
       - name: Build and push container
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: .devcontainer/Dockerfile