The Obama administration has decided to jettison CGI Federal, the main IT contractor that was responsible for building the defect-ridden online health insurance marketplace and has been immersed in the work of repairing it. Federal health officials are preparing to sign a 12-month contract worth roughly $90 million, probably early next week, with a different company, Accenture, after concluding that CGI has not been effective enough in fixing the intricate computer system underpinning the federal Web site, HealthCare.gov. Accenture, which is one of the world’s largest consulting firms, has extensive experience with computer systems on the state level, and it...