Japan’s antitrust watchdog has found that a Toyota Motor Corp. subsidiary forced about 50 subcontractors to store auto parts molds without paying the costs and plans to warn the group company to take measures to prevent a recurrence, a source familiar with the matter said Sunday. Toyota Customizing & Development Co., in which Toyota holds a 90.5 percent stake, has admitted to violating the subcontract law, the sources said. The subsidiary, which makes auto parts, ambulances and racing cars, allegedly forced around 50 suppliers to retain more than 650 molds and inspection instruments for parts …