New J2K: do not save import statements in files as we print fqNames for calls

This may cause conflicts on shortening fq references post-processing step

nj2k/testData/newJ2k/mutableCollections/mutableListInOtherClass.kt

@@ -1,5 +1,3 @@
-import java.util.ArrayList
-
 class Owner {
     var list: MutableList<String> = ArrayList()
 }
@@ -8,4 +6,4 @@ class Updater {
     fun update(owner: Owner) {
         owner.list.add("")
     }
-}
+}