chore(deps): Bump docker/build-push-action from 6.12.0 to 6.13.0 (#4331)

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.12.0 to 6.13.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](https://github.com/docker/build-push-action/compare/v6.12.0...v6.13.0)

---
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>
Co-authored-by: Georg Lauterbach <44545919+georglauterbach@users.noreply.github.com>

.github/workflows/generic_build.yml

@@ -80,7 +80,7 @@ jobs:
 
       # NOTE: AMD64 can build within 2 minutes
       - name: 'Build images'
-        uses: docker/build-push-action@v6.12.0
+        uses: docker/build-push-action@v6.13.0
         with:
           context: .
           # Build at least the AMD64 image (which runs against the test suite).

.github/workflows/generic_publish.yml

@@ -67,7 +67,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: 'Build and publish images'
-        uses: docker/build-push-action@v6.12.0
+        uses: docker/build-push-action@v6.13.0
         with:
           context: .
           build-args: |

.github/workflows/generic_test.yml

@@ -43,7 +43,7 @@ jobs:
       # Importing from the cache should create the image within approx 30 seconds:
       # NOTE: `qemu` step is not needed as we only test for AMD64.
       - name: 'Build AMD64 image from cache'
-        uses: docker/build-push-action@v6.12.0
+        uses: docker/build-push-action@v6.13.0
         with:
           context: .
           tags: mailserver-testing:ci

.github/workflows/generic_vulnerability-scan.yml

@@ -42,7 +42,7 @@ jobs:
       # Importing from the cache should create the image within approx 30 seconds:
       # NOTE: `qemu` step is not needed as we only test for AMD64.
       - name: 'Build AMD64 image from cache'
-        uses: docker/build-push-action@v6.12.0
+        uses: docker/build-push-action@v6.13.0
         with:
           context: .
           tags: mailserver-testing:ci