Downgrade to java 21

MaartenS11 · MaartenS11 · commit 026465175cc0 · 2026-04-13T17:10:14.000+02:00
22 is a strange version that is hard to get, 21 is an LTS, we could also use 25 but that's not available everywhere
diff --git a/build.gradle.kts b/build.gradle.kts
@@ -42,7 +42,7 @@ tasks.test {
 }
 
 kotlin {
-    jvmToolchain(22)
+    jvmToolchain(21)
 }
 
 application {
