style(amplify-codegen): adds a todo comment (#820)

Adds todo to clean up Dart codegen in next major version bump

Author: Equartey

packages/appsync-modelgen-plugin/src/visitors/appsync-dart-visitor.ts

@@ -448,6 +448,8 @@ export class AppSyncModelDartVisitor<
 
   protected generateGetters(model: CodeGenModel, declarationBlock: DartDeclarationBlock, includeIdGetter: boolean = true): void {
     if (includeIdGetter) {
+      // TODO: Remove at the next major version.
+      // Amplify Flutter V2 removes all usage of Model.getId() in favor of Model.modelIdentifier
       if (this.isCustomPKEnabled()) {
         const identifierFields = this.getModelIdentifierFields(model);
         const isCustomPK = identifierFields[0].name !== 'id';