CI: Run jruby jobs on kubernetes cluster

Author: bastelfreak

.github/workflows/tests.yaml

@@ -45,8 +45,8 @@ jobs:
           - {os: ubuntu-24.04, ruby: '3.2'}
           - {os: ubuntu-24.04, ruby: '3.3'}
           - {os: ubuntu-24.04, ruby: '3.4'}
-          - {os: ubuntu-24.04, ruby: 'jruby-9.4.8.0'}
-          - {os: ubuntu-24.04, ruby: 'jruby-9.4.14.0'}
+          - {os: runnerset-voxpupuli, ruby: 'jruby-9.4.8.0'}
+          - {os: runnerset-voxpupuli, ruby: 'jruby-9.4.14.0'}
           - {os: windows-2025, ruby: '3.2'}
           - {os: windows-2025, ruby: '3.3'}
           - {os: windows-2025, ruby: '3.4'}