Update transactions.md (#3823)

Under the 'Share Connection and transaction' section, the 3rd highlight is on the wrong line. Instead of highlighting the `UseTransaction`, it highlights the opening curly bracket.

Author: eersonmez

entity-framework/core/saving/transactions.md

@@ -82,7 +82,7 @@ public class BloggingContext : DbContext
 
 You can now create multiple context instances that share the same connection. Then use the `DbContext.Database.UseTransaction(DbTransaction)` API to enlist both contexts in the same transaction.
 
-[!code-csharp[Main](../../../samples/core/Saving/Transactions/SharingTransaction.cs?name=Transaction&highlight=1-3,6,14,21-23)]
+[!code-csharp[Main](../../../samples/core/Saving/Transactions/SharingTransaction.cs?name=Transaction&highlight=1-4,7,15,22-24)]
 
 ## Using external DbTransactions (relational databases only)