fix(transformers): record reflection info about abstract classes

Closes #7347

modules_dart/transform/lib/src/transform/common/code/reflection_info_code.dart

@@ -67,7 +67,6 @@ class ReflectionInfoVisitor extends RecursiveAstVisitor<ReflectionInfoModel> {
 
   @override
   ReflectionInfoModel visitClassDeclaration(ClassDeclaration node) {
-    if (node.isAbstract) return null;
     if (!node.metadata
         .any((a) => _annotationMatcher.hasMatch(a.name, assetId))) {
       return null;