Update Docker build platforms in workflow

Reduced the target platforms for Docker builds to only amd64 and arm64.

Author: lisaac

.github/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
         uses: docker/build-push-action@v2
         with:
           context: .
-          platforms: linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64,linux/ppc64le,linux/s390x
+          platforms: linux/amd64,linux/arm64
           push: true
           file: container/Dockerfile.nano
           tags: lisaac/luci:nano
@@ -38,7 +38,7 @@ jobs:
         uses: docker/build-push-action@v2
         with:
           context: .
-          platforms: linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64,linux/ppc64le,linux/s390x
+          platforms: linux/amd64,linux/arm64
           push: true
           file: container/Dockerfile
           tags: lisaac/luci:latest