kinterbasdb download link is not up-to-date

[Former user]

In the http://www.sqlalchemy.org/docs/dbengine.html page the firebirdsql dbdriver points to the old, not maintained http://kinterbasdb.sourceforge.net/ link instead of http://firebirdsql.org/index.php?op=devel&sub=python which hosts the latest official release.

[Lele Gaifax]

Done in 6739.