Bump ubuntu runner version (#667)

Author: stympy

.github/workflows/ruby.yml

@@ -71,7 +71,7 @@ jobs:
         bundle exec rake
 
   jruby:
-    runs-on: ubuntu-20.04 # ubuntu-latest is currently 22.04, which doesn't have a supported JRuby 9 build yet
+    runs-on: ubuntu-22.04
     timeout-minutes: 10
     strategy:
       matrix: