KAPT: Skip importing java.lang.System in the stubs

This fixes KT-43117

plugins/kapt3/kapt3-compiler/testData/converter/defaultParameterValueOff.txt

@@ -1,5 +1,3 @@
-import java.lang.System;
-
 @kotlin.Metadata()
 public enum Em {
     /*public static final*/ FOO /* = new Em() */,
@@ -12,8 +10,6 @@ public enum Em {
 ////////////////////
 
 
-import java.lang.System;
-
 @kotlin.Metadata()
 public final class Foo {
     private final boolean z = false;