Fix bad CI image name

Author: SeanTAllen

.github/workflows/breakage-against-ponyc-latest.yml

@@ -9,7 +9,7 @@ jobs:
     name: Test against ponyc main
     runs-on: ubuntu-latest
     container:
-      image: ponylang/x86-64-unknown-linux-builder-with-libressl-3.2.5:latest
+      image: ponylang/shared-docker-ci-x86-64-unknown-linux-builder-with-libressl-3.2.5:latest
     steps:
       - uses: actions/checkout@v1
       - name: Test