Fix code reference

Fixes #4871

Author: roji

samples/core/Miscellaneous/NewInEFCore9/QuerySample.cs

@@ -215,7 +215,7 @@ async Task<List<Post>> GetPostsForceConstantCollection(int[] ids)
         Console.WriteLine();
         Console.WriteLine("Aggregate over subquery/aggregate:");
         Console.WriteLine();
-        // </AggregateOverSubquery>
+        #region AggregateOverSubquery
         var latestPostsAverageRatingByLanguage = await context.Blogs.
             Select(x => new
             {
@@ -225,7 +225,7 @@ async Task<List<Post>> GetPostsForceConstantCollection(int[] ids)
             .GroupBy(x => x.Language)
             .Select(x => x.Average(xx => xx.LatestPostRating))
             .ToListAsync();
-        // </AggregateOverSubquery>
+        #endregion
 
         // Max over decimal is not supported on Sqlite
         if (!context.UseSqlite)