Updated only place still using 20.04. - I assume this breaks something, let's see what

Author: RandomDefaultUser

.github/workflows/cpu-tests.yml

@@ -118,7 +118,7 @@ jobs:
 
   cpu-tests:
     needs: build-docker-image-cpu
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     env:
       IMAGE_REPO: ${{ needs.build-docker-image-cpu.outputs.image-repo }}
       DOCKER_TAG: ${{ needs.build-docker-image-cpu.outputs.docker-tag }}