Is it still necessary to check for a front camera?
According to the iOS Device Compatibility Reference, the iPhone 3GS was the only iOS 6-capable device to lack a front camera.

The same document states that your application can declare the requirement for a front-facing camera by setting the UIRequiredDeviceCapabilities key such that front-facing-camera is true.  That way, you can safely strip out the camera-checking code while having your application self-document the assumption that the front camera exists.