use a docker image in GH workflow

Author: parmentelat

.github/workflows/myst-to-pages.yml

@@ -38,19 +38,13 @@ concurrency:
 jobs:
   build-and-deploy:
     runs-on: self-hosted
+    container:
+      image: ghcr.io/prefix-dev/pixi:latest
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
         with:
           clean: true
-      - name: Clean up previous pixi installation
-        run: |
-          rm -rf /containers/github-actions/.pixi || true
-      - name: Setup pixi
-        uses: prefix-dev/setup-pixi@v0.8.1
-        with:
-          pixi-version: latest
-          cache: true
       - name: Setup dependencies
         run: |
           pixi install