First off, it always recommended that you use supported environments. You should set up a database environment that is a supported version rather than trying to work with an unsupported version. Other problems may arise from your use of an unsupported database version.
Given that, I have read about creating exception files to ignore some errors that may be raised during project upgrade verification. One such thread is
http://h30499.www3.hp.com/t5/Quality-Center-Support-Customer/lt-QC-ALM-Support-Tip-gt-How-to-define-an-Exception-File-in/m-p/6272731/highlight/true#M1575
It references an HP support article
http://support.openview.hp.com/selfsolve/document/KM00654227
The thread didn't specifically mention the database version error, so I don't know how that error specifically would be ignored.
This other thread might also help.
http://h30499.www3.hp.com/t5/Quality-Center-Support-and-News/QC10-and-SQL-Server-2008/m-p/4431410/highlight/true#M21715