default -> companion: replace all mentions of default and default object

compiler/testData/diagnostics/tests/inference/regressions/kt702.kt

@@ -5,7 +5,7 @@ package a
 fun getJavaClass<T>() : java.lang.Class<T> { <!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
 
 public class Throwables() {
-    default object {
+    companion object {
         public fun propagateIfInstanceOf<X : Throwable?>(throwable : Throwable?, declaredType : Class<X<!BASE_WITH_NULLABLE_UPPER_BOUND!>?<!>>?) : Unit {
             if (((throwable != null) && declaredType?.isInstance(throwable)!!))
             {