[Build] Add jUnit dependencies in testApiJUnit5 to the implementation configuration

Adding these dependencies to the `api` configuration pollutes classpath for each dependant modules even if it doesn't need them. Instead, the dependencies should be declared more granularly if they're required
#KTI-1349 In Progress

plugins/assign-plugin/build.gradle.kts

@@ -20,12 +20,13 @@ dependencies {
     testApi(projectTests(":compiler:tests-common-new"))
 
     testImplementation(projectTests(":compiler:tests-common"))
-    testImplementation(libs.junit4)
+    testImplementation(libs.junit.jupyter.api)
 
     testCompileOnly(project(":kotlin-reflect-api"))
     testRuntimeOnly(project(":kotlin-reflect"))
     testRuntimeOnly(project(":core:descriptors.runtime"))
     testRuntimeOnly(project(":compiler:fir:fir-serialization"))
+    testRuntimeOnly(libs.junit.jupyter.engine)
 
     testApi(intellijCore())
 }