BERKELEY, Calif. — Apple has agreed to let developers of iPhone apps email their users about cheaper ways to pay for digital subscriptions and media by circumventing a commission system that generates billions of dollars annually for the iPhone maker.The concession announced late Thursday, which covers emailed notifications but does not allow in-app notifications, is part of a preliminary settlement of a nearly 2-year-old lawsuit filed on behalf of iPhone app developers in the U.S. It also addresses an issue raised by a …