update runner instance

Author: bnusunny

.github/workflows/security_audit.yaml

@@ -4,9 +4,9 @@ on:
     - cron: '0 0 * * *'
 jobs:
   audit:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: rustsec/[email protected]
         with:
           token: ${{ secrets.GITHUB_TOKEN }}