Revert "test"

This reverts commit ef47d68.

Author: LiamHamsters

src/Ydb.Sdk/src/Ado/YdbCommand.cs

@@ -210,7 +210,7 @@ protected override async Task<DbDataReader> ExecuteDbDataReaderAsync(CommandBeha
             ? new GrpcRequestSettings { TransportTimeout = TimeSpan.FromSeconds(CommandTimeout) }
             : new GrpcRequestSettings();
 
-        var transaction = Transaction ?? YdbConnection.CurrentTransaction;
+        var transaction = YdbConnection.CurrentTransaction;
 
         if (Transaction != null && Transaction != transaction)
         {

src/Ydb.Sdk/src/Ado/YdbConnection.cs

@@ -72,17 +72,8 @@ public YdbTransaction BeginTransaction(TransactionMode transactionMode = Transac
         if (CurrentTransaction is { Completed: false })
         {
             throw new InvalidOperationException(
-                "A transaction is already in progress; nested/concurrent transactions aren't supported.");
-        }
-
-        if (Session is ImplicitSession)
-        {
-            var driver = Session.Driver;
-            Session.Dispose();
-
-            var factory = new PoolingSessionFactory(driver, ConnectionStringBuilder);
-            var pooledSource = new PoolingSessionSource<PoolingSession>(factory, ConnectionStringBuilder);
-            Session = pooledSource.OpenSession(CancellationToken.None).GetAwaiter().GetResult();
+                "A transaction is already in progress; nested/concurrent transactions aren't supported."
+            );
         }
 
         CurrentTransaction = new YdbTransaction(this, transactionMode);