remove buildx setup since Makefile handles this

Author: mallardduck

.github/workflows/ci.yml

@@ -41,8 +41,6 @@ jobs:
         # https://github.com/docker/setup-qemu-action
         name: Set up QEMU
         uses: docker/setup-qemu-action@v3
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@b5ca514318bd6ebac0fb2aedd5d36ec1b5c232a2 # v3 
       - name: Check out repository code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Basic CI