Remove JDK 23 from 2.18 CI due to Mockito incompatibility

Author: cowtowncoder

.github/workflows/main.yml

@@ -18,7 +18,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java_version: ['8', '11', '17', '21', '23']
+        # 10-Jun-2025, tatu: JDK 23 fails for Mockito, don't use
+        java_version: ['8', '11', '17', '21']
         os: ['ubuntu-24.04']
         include:
           - java_version: '8'