disabling flawfinder-sast

the pipeline in https://gitlab.com/nunet/device-management-service/-/pipelines/1270896982 fails with 'flawfinder-defectdojo' job needs 'flawfinder-sast' job, but 'flawfinder-sast' is not in any previous stage

There isn't a clear reason why flawfinder-sast isn't triggered while flawfinder-defectdojo is. Even changing both jobs to use the same rules, flawfinder-sast still won't execute.

This MR disables flawfinder completely so that while the investigation continues, the pipeline can be run again.