[fix] CI: container-mounts bad hash

This is a typo, but if there are multiple patterns in hashFiles, they should be separated by commas.

https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/evaluate-expressions-in-workflows-and-actions#examples-with-multiple-patterns

.github/workflows/container.yml

@@ -76,7 +76,7 @@ jobs:
         uses: actions/cache@v4
         with:
           # yamllint disable-line rule:line-length
-          key: "container-mounts-${{ matrix.arch }}-${{ hashFiles('./container/Dockerfile ./container/legacy/Dockerfile') }}"
+          key: "container-mounts-${{ matrix.arch }}-${{ hashFiles('./container/Dockerfile', './container/legacy/Dockerfile') }}"
           restore-keys: "container-mounts-${{ matrix.arch }}-"
           path: |
             /var/tmp/buildah-cache/