Fix rightButton margin is not correctly set when autoHideRightButton = NO
Fix rightButton margin is not correctly set when autoHideRightButton = NO

https://github.com/slackhq/SlackTextViewController/commit/dceedc70393e873d70c82da39c9f2cc9f18fda5a#diff-592522ed60e49c6ca08c23b1fa1ac14aR104 broke the behavior.

kobim/SlackTextViewController,kobim/SlackTextViewController,slackhq/SlackTextViewController,slackhq/SlackTextViewController