Do not add nullability annotations to the methods of anonymous classes

Nullability annotations are useless for the methods of anonymous classes
due to their restricted scope.

^KT-62044: Fixed

plugins/atomicfu/atomicfu-compiler/testData/box/atomics_basic/SimpleLockTest.txt

@@ -21,7 +21,7 @@ final class SimpleLockTest$withLock$result$1 {
     static method <clinit>(): void
     method <init>(): void
     public synthetic bridge method invoke(): java.lang.Object
-    public final @org.jetbrains.annotations.NotNull method invoke(): java.lang.String
+    public final method invoke(): java.lang.String
 }
 
 @kotlin.Metadata