I mistakenly put some of the styles for the `MessageActionButtons` (reply, create sidebar, etc) in the `ComposedMessage` stylesheet instead of in the `MessageActionButtons` stylesheet. This meant that the `MessageActionButtons` component was appearing incorrectly for `RobotextMessage`s.
This diff puts the `MessageActionButtons`-related styling at the right layer of abstraction and fixes how things look for robotext messages.