Update dart.yml

Author: dave-doty

.github/workflows/dart.yml

@@ -24,7 +24,7 @@ jobs:
 
   fail_if_pull_request_is_draft:
     if: github.event.pull_request.draft == true
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Fails in order to indicate that pull request needs to be marked as ready to review and unit tests workflow needs to pass.
         run: exit 1