bring back ci testing of dependencies

Author: gggeek

.github/workflows/ci.yaml

@@ -153,7 +153,7 @@ jobs:
     # so that we can catch any (involuntary) breakage.
     # NB: if any are detected, do not forget to mark the current versions of dependents as incompatible in composer.json
     test-dependencies:
-        runs-on: ubuntu-20.04
+        runs-on: ubuntu-22.04
         strategy:
             fail-fast: false
             matrix: