workflow syntax fix

Signed-off-by: Geoff Wilson <geoff@gr-oss.io>

Author: suprjinx

.github/workflows/ci.yml

@@ -10,12 +10,13 @@ on:
 jobs:
 
   prepare_image:
-    - name: Pre-build dev container image
-      uses: devcontainers/ci@v0.3
-      with:
-        imageName: ghcr.io/G-Research/pulp-manager-devcontainer
-        cacheFrom: ghcr.io/G-Research/pulp-manager-devcontainer
-        push: always
+    steps:
+      - name: Pre-build dev container image
+        uses: devcontainers/ci@v0.3
+        with:
+          imageName: ghcr.io/G-Research/pulp-manager-devcontainer
+          cacheFrom: ghcr.io/G-Research/pulp-manager-devcontainer
+          push: always
 
   lint:
     name: Lint