build(mps-model-adapters): fixed inconsistent JVM target setting

It fixes this error message:

Execution failed for task ':mps-model-adapters-plugin:compileTestKotlin'.
> Inconsistent JVM-target compatibility detected for tasks 'compileTestJava' (11) and 'compileTestKotlin' (17).

Author: slisson

mps-model-adapters-plugin/build.gradle.kts

@@ -1,5 +1,4 @@
 import org.modelix.copyMps
-import org.modelix.mpsJavaVersion
 
 plugins {
     kotlin("jvm")
@@ -17,10 +16,6 @@ intellij {
 }
 
 tasks {
-    withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-        kotlinOptions.jvmTarget = mpsJavaVersion.toString()
-    }
-
     patchPluginXml {
         sinceBuild.set("211")
         untilBuild.set("241.*")