ci: add jdk23 to test matrix

Author: lread

.github/workflows/tests.yml

@@ -44,7 +44,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [{name: 'windows', shell: 'pwsh'}, {name: 'ubuntu', shell: 'bash'}]
-        jdk: ['8', '11', '17', '21']
+        jdk: ['8', '11', '17', '21', '23']
 
     name: ${{matrix.os.name}} - jdk ${{ matrix.jdk }}