Update versions for CI

Author: k163377

.github/workflows/test-main.yml

@@ -40,9 +40,9 @@ jobs:
       fail-fast: false
       matrix:
         # LTS versions, latest version (if exists)
-        java-version: [ '17', '21', '25' ]
+        java-version: [ '17', '21', '25', '26' ]
         # Minimum version, latest release version, latest pre-release version (if exists)
-        kotlin: ['2.1.21', '2.2.21', '2.3.0-RC2']
+        kotlin: ['2.1.21', '2.2.21', '2.3.20']
     env:
       KOTLIN_VERSION: ${{ matrix.kotlin }}
     name: "Kotlin ${{ matrix.kotlin }} - Java ${{ matrix.java-version }}"