Undo upgrade testing change.

This workflow should only ever run in `trunk`.

Author: desrosj

.github/workflows/upgrade-testing.yml

@@ -62,7 +62,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ 'ubuntu-latest' ]
+        os: [ 'ubuntu-24.04' ]
         php: [ '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4' ]
         db-type: [ 'mysql' ]
         db-version: [ '5.7', '8.0', '8.4', '9.1' ]