[microsoft#1184](microsoft#1184) : Use the 6th version of docker/build-push-action

I don't see why v5 should be used instead of v6 ?
Also, the [most recent `docker/build-push-action`](https://github.com/docker/build-push-action/blob/88844b95d8cbbb41035fa9c94e5967a33b92db78/README.md?plain=1#L53-L81)'s README tell us that version compatibility with the other actions is not an issue

Author: goulvenb

.github/workflows/docker.yml

@@ -38,7 +38,7 @@ jobs:
           images: ghcr.io/${{ github.repository }}
 
       - name: Build and push Docker image (multi-arch)
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./Dockerfile