Change "SQL Server vNext" references to 2019

[BrentOzar]

Do you want to request a feature or report a bug?
Bug, but not intentional - just need to update the scripts with the new 15 version number. I'll do a pull request for it - I'm not that bright, but it's easy work, ha ha ho ho.

What is the current behavior?
The vNext folder doesn't work on SQL Server 2019 because it's checking for 14 as the version number in lines like this:

-- Ensure that we are running SQL Server vNext
if substring(@SQLServerVersion,1,CHARINDEX('.',@SQLServerVersion)-1) <> N'14'
begin
	set @errorMessage = (N'You are not running a SQL Server vNext. Your SQL Server version is ' + @SQLServerVersion);
	Throw 51000, @errorMessage, 1;
end

What is the expected behavior?
Check for version number >= 15 (just aiming for future compatibility) and say 2019 rather than vNext.

Which versions of SQL Server and which OS are affected by this issue? Did this work in previous versions of our procedures?
Just SQL Server 2019, and hasn't worked since 2019 RTM.

[ZedZipDev]

What about SQL 2022 ?