Drop jruby-9.4.13.0 testing

Since we test against jruby-9.4.14.0 now, we don't need to test against jruby-9.4.13.0. At the moment we package jruby-9.4.8. We add the latest version because that's the potential target for the next release.

Author: bastelfreak

.github/workflows/tests.yaml

@@ -46,7 +46,6 @@ jobs:
           - {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-9.4.13.0'}
           - {os: ubuntu-24.04, ruby: 'jruby-9.4.14.0'}
           - {os: windows-2025, ruby: '3.2'}
           - {os: windows-2025, ruby: '3.3'}