ci: install docker CLI in image-pull job

.gitea/workflows/ci.yml

@@ -66,6 +66,7 @@ jobs:
 
       - name: Pull changed images
         run: |
+          apt-get install -y docker.io -qq
           git fetch origin ${{ github.base_ref }}
           IMAGES=$(git diff origin/${{ github.base_ref }}...HEAD -- '*.nomad.hcl' \
             | grep '^+\s*image\s*=' \