Revert "Change to self-hosted runner"

This reverts commit b2fef15.

.github/workflows/regression.yml

@@ -16,7 +16,7 @@ concurrency:
 jobs:
   build:
     name: Regression Testing
-    runs-on: self-hosted
+    runs-on: ubuntu-latest
     if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     steps:
       - uses: actions/checkout@v4