Fix subgraph-test job (#928)

The Github Actions migrates the `ubuntu-latest` label to `ubuntu 24` see
https://github.blog/changelog/2024-12-05-notice-of-upcoming-releases-and-breaking-changes-for-github-actions/

The subgraph does not support all platforms so we change the `runs-on`
to `ubuntu-22.04`.

.github/workflows/subgraph.yaml

@@ -97,7 +97,7 @@ jobs:
 
   subgraph-test:
     needs: [subgraph-codegen]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     steps:
       - uses: actions/checkout@v4