Rename package in JPS plugin tests

Package 'kotlin' is not supported until package views are implemented, because
its name clashes with the stdlib

jps-plugin/testData/JKJInheritanceProject/src/java/JSecond.java

@@ -1,7 +1,7 @@
 package java;
 
-public class JSecond extends kotlin.KFirst {
+public class JSecond extends kt.KFirst {
     public void bar() {
         foo();
     }
-}
+}

jps-plugin/testData/JKJInheritanceProject/src/kotlin/KFirst.kt

@@ -1,5 +1,5 @@
-package kotlin
+package kt
 
 open class KFirst(): java.JFirst() {
 
-}
+}