Switch driver dependency

[gandaldf]

The official support for the MSSQL driver has moved to Microsoft. It might be a good idea to switch to the new repository: https://github.com/microsoft/go-mssqldb

[bokwoon95]

Oh don't worry about it, github.com/denisenkom/go-mssqldb is only a test dependency to test SQL Server queries. sq itself doesn't import any sql driver, it is up to the user to do so. If anything, using the old driver serves as a litmus test to see if the old driver still works (at least for simple queries).