Switch old branch ci.yml to use ubuntu-latest, due to gh deprecating ubuntu-20.04

Author: zlovatt

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   pages:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}