ci: use docker instead of podman for cooklang validation

.gitea/workflows/validate-cooklang.yml

@@ -1,5 +1,5 @@
 # Validates that all .cook files in this repository are valid Cooklang recipes.
-# Uses cookcli (https://hub.docker.com/r/inigochoa/cookcli) via Podman.
+# Uses cookcli (https://hub.docker.com/r/inigochoa/cookcli) via Docker.
 name: Validate Cooklang
 
 on:
@@ -16,7 +16,7 @@ jobs:
 
       - name: Validate all .cook files
         run: |
-          podman run --rm \
+          docker run --rm \
             -v "$(pwd):/recipes:ro" \
             docker.io/inigochoa/cookcli \
             cook doctor validate -b /recipes --strict