Use shell commands for fetching repo instead

Did not work as expected with the checkout action (it is trying to use
auth etc).

.forgejo/workflows/container.yaml

@@ -7,10 +7,9 @@ jobs:
       REMOTE_CODE_REF: '15e7af41fb56b4f19e1b6312cdd3fc697f1c0fc8'
     steps:
       - uses: https://code.forgejo.org/actions/checkout@v4
-        with:
-          repository: 'SUNET/sunet-vcl-validator'
-          github-server-url: 'https://github.com'
-          ref: ${{ env.REMOTE_CODE_REF }}
+      - run: |
+            git clone https://github.com/SUNET/sunet-vcl-validator.git
+            git checkout ${{ env.REMOTE_CODE_REF }}
       - uses: https://platform.sunet.se/sunet-cdn/runner-action-kaniko@2088faeaa6a22c2f85b61a7b41cdecf4f83cf36a
         with:
           credential: ci-sunet-cdn:${{ secrets.CI_SUNET_CDN }}