fix: github action runner not exist (#477)

- ubuntu-20.04 is already deprecated
- use ubunut-latest to dynamically use latest version


(cherry picked from commit 80ac25b)

Signed-off-by: Wen Zhou <wenzhou@redhat.com>

Author: zdtsw

.github/workflows/re-run-action.yml

@@ -8,7 +8,7 @@ jobs:
   rerun_pr_tests:
     name: rerun_pr_tests
     if: ${{ github.event.issue.pull_request }}
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
     - uses: estroz/rerun-actions@main
       with: