[native] Center "no media found" error in MediaGalleryKeyboard

Summary: For some reason this is the only one we weren't applying bottomOffsetStyle to, so it wasn't accounting for the safe area bottom offset when centering the error message.

Test Plan: Make sure the error message is centered, and appears in same vertical position as the ActivityIndicator

Reviewers: atul, palys-swm

Reviewed By: atul

Subscribers: KatPo, zrebcu411, Adrian, subnub

Differential Revision: https://phabricator.ashoat.com/D925