Fix CI failures by pining the ubuntu version for backend CI (#3194)

The ubuntu-latest image has been updated to 24.04 from 22.04 in recent
days. However, the new image is incompatible with libncurses5, requiring
an upgrade to libncurses6. Unfortunately, after upgrading, sbt no longer
functions as expected, an issue also documented here:
[actions/setup-java#712](actions/setup-java#712).
It appears that the 24.04 image does not include sbt by default.

This PR addresses the issue by pinning the image to ubuntu-22.04. We can
revisit and update the version when the 24.04 image becomes more stable
and resolves these compatibility problems.

.github/workflows/github-action-build.yml

@@ -56,7 +56,7 @@ jobs:
   core:
     strategy:
       matrix:
-        os: [ ubuntu-latest ]
+        os: [ ubuntu-22.04 ]
         java-version: [ 11 ]
     runs-on: ${{ matrix.os }}
     env: