CI: Dont build packages in a Ruby matrix

Author: bastelfreak

.github/workflows/pr-testing.yml

@@ -93,7 +93,7 @@ jobs:
       fail-fast: false
       matrix:
         java: ['11', '17', '21']
-        ruby: ['3.2', '3.3']
+        ruby: ['3.3']
     steps:
       - name: checkout repo
         uses: actions/checkout@v5