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

compiler/testData/serialization/builtinsSerializer/annotationTargets.kt

@@ -32,6 +32,6 @@ class C1 [anno("constructor")] () {
     anno("nested class")
     class C2
 
-    anno("default object")
-    default object {}
+    anno("companion object")
+    companion object {}
 }

compiler/testData/serialization/builtinsSerializer/annotationTargets.txt

@@ -16,8 +16,8 @@ test.anno(x = "top level class": kotlin.String) internal final class C1 {
         public constructor C2()
     }
 
-    test.anno(x = "default object": kotlin.String) internal default object Default {
-        private constructor Default()
+    test.anno(x = "companion object": kotlin.String) internal companion object Companion {
+        private constructor Companion()
     }
 }