CI: Remove jruby 9.4.8 testing

Our openvox-server has 9.4.12.1, we don't need to test on the older
version anymore.

```
[root@pe ~]# dnf info openvox-server
Last metadata expiration check: 0:00:04 ago on Sun 15 Feb 2026 06:38:55 PM UTC.
Installed Packages
Name         : openvox-server
Version      : 8.12.1
Release      : 1.el10
Architecture : noarch
Size         : 79 M
Source       : openvox-server-8.12.1-1.el10.src.rpm
Repository   : @System
From repo    : openvox8
Summary      : Vox Pupuli puppetserver
URL          : http://github.com/openvoxproject
License      : ASL 2.0
Description  : Vox Pupuli puppetserver
             : Contains: OpenVox Server (org.openvoxproject/puppetserver 8.12.1,org.clojure/clojure
             : 1.12.4,org.bouncycastle/bcpkix-jdk18on 1.83,org.openvoxproject/jruby-utils
             : 5.3.6,org.openvoxproject/puppetserver
             : 8.12.1,org.openvoxproject/trapperkeeper-webserver-jetty10
             : 1.1.4,org.openvoxproject/trapperkeeper-metrics 2.1.7)

[root@pe ~]# /opt/puppetlabs/server/bin/puppetserver ruby --version
jruby 9.4.12.1 (3.1.4) 2025-05-07 64b3479ca4 OpenJDK 64-Bit Server VM 21.0.10+7-LTS on 21.0.10+7-LTS +jit [x86_64-linux]
[root@pe ~]#
```

Author: bastelfreak

.github/workflows/ci.yaml

@@ -39,7 +39,6 @@ jobs:
         ruby: ${{ fromJSON(needs.rubocop_and_matrix.outputs.ruby) }}
         include:
           - ruby: 'jruby-9.4.12.1'
-          - ruby: 'jruby-9.4.8.0'
           - ruby: 'jruby-10.0.2.0'
     runs-on: ubuntu-24.04
     steps:
@@ -140,7 +139,6 @@ jobs:
           - {os: ubuntu-latest, ruby: '2.7'}
           - {os: ubuntu-22.04, ruby: '3.2'} # with openssl 3
           - {os: ubuntu-22.04, ruby: 'jruby-9.3.14.0'}
-          - {os: ubuntu-latest, ruby: 'jruby-9.4.8.0'}
           - {os: ubuntu-latest, ruby: 'jruby-9.4.12.1'}
           - {os: ubuntu-latest, ruby: 'jruby-10.0.2.0'}
           - {os: windows-2022, ruby: '2.7'}