Replace kotlin-test project dependencies in the project

Use dependency helper function that chooses whether to take them
from the bootstrap repository or from a configuration of kotlin-test

KT-61969

libraries/examples/kotlin-gradle-subplugin-example/build.gradle

@@ -17,8 +17,6 @@ dependencies {
     // Use this dependency instead when building apart from the other modules:
     // compile "org.jetbrains.kotlin:kotlin-gradle-plugin-api:$kotlin_version"
 
-    api project(':kotlin-test:kotlin-test-junit')
-
     compileOnly RepoDependencies.kotlinStdlib(project)
     compileOnly project(':compiler')
     compileOnly project(':compiler:plugin-api')