[FE Test] Rename nested directory in testdata into nestedClasses

This is needed to avoid clash between generated test class `Nested` and
  `@Nested` annotation from JUnit 5

compiler/testData/loadJava/compiledKotlin/nestedClasses/innerClassReferencesOuterTP.kt

@@ -0,0 +1,5 @@
+package test
+
+class InnerClassReferencesOuterTP<P> {
+    inner class Inner<Q : P>
+}