removed not needed "using"

Author: DevM900

src/FirebirdSql.Data.FirebirdClient/Common/Extensions.cs

@@ -20,8 +20,6 @@
 using System.IO;
 using System.Linq;
 using System.Net.Sockets;
-using System.Security.Cryptography;
-using System.Text;
 
 namespace FirebirdSql.Data.Common;