Undo change to Kotlin versions to test on CI

Author: cowtowncoder

.github/workflows/main.yml

@@ -25,11 +25,12 @@ jobs:
     runs-on: 'ubuntu-22.04'
     strategy:
       fail-fast: false
+      max-parallel: 5
       matrix:
         java_version: ['8', '11', '17', '21', '22']
         # kotlin-reflect 1.8.2x has a bug and some tests fail, so we are downgrading to 1.8.10.
         # kotlin-reflect 2.0.0-Beta5 is not used because of KT-67209
-        kotlin_version: ['1.7.22', '1.8.10', '1.9.23', '2.0.0-RC2']
+        kotlin_version: ['1.7.22', '1.8.10', '1.9.23', '2.0.0-Beta4']
         include:
           - java_version: '8'
             kotlin_version: '1.7.22'