Update Jekyll build to Ubuntu 24.04

Author: dyfer

.github/workflows/jekyll.yml

@@ -13,7 +13,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     name: 'jekyll build'
     env:
       # use BUNDLE_ env vars to set 'bundle config' options