Fix typo in exception message.

Author: bgrainger

src/MySqlConnector/MySql.Data.MySqlClient/MySqlCommand.cs

@@ -130,7 +130,7 @@ private bool NeedsPrepare(out Exception? exception)
 
 			if (CommandType != CommandType.StoredProcedure && CommandType != CommandType.Text)
 			{
-				exception = new NotSupportedException("Only CommandType.Text and CommandType.StoredProcedure is currently supported by MySqlCommand.Prepare");
+				exception = new NotSupportedException("Only CommandType.Text and CommandType.StoredProcedure are currently supported by MySqlCommand.Prepare.");
 				return false;
 			}