Remove bitcode support from engine

[jmagman]

Once bitcode support has been removed from Flutter tooling #107883, remove --bitcode from the gn script and any other relevant logic.

Starting with Xcode 14, bitcode is no longer required for watchOS and tvOS applications, and the App Store no longer accepts bitcode submissions from Xcode 14.

See #15288 and flutter/engine#9823 when bitcode was introduced.