Fix the documentation "Connecting JIRA applications to SQL Server 2012" for JIRA 7.5.x

Problem Definition

Since 7.5.x, JIRA is shipped with a new JDBC driver for Microsoft SQL Server.

Because of this change, the format of the file dbconfig.xml file needs to be changed (for example, the prefix of the database URL is now 'jdbc:sqlserver://')

The documentation Connecting JIRA applications to SQL Server 2012 needs to be updated for Server 7.5 to reflect this change (the sample dbconfig.xml file needs to be updated as well in this documentation).

Why this is important

If the dbconfig.xml file is not properly configured, customers can't connect to the MS SQL database.
It can be problematic when a customer upgrades from a version below 7.5 to 7.5.

Workaround

For now, there is a KB that explains how to update the dbconfig.xml file Updating JDBC URL for Microsoft SQL Server