Move text style tools out of experimental

These were meant to have been de-experimental-ised with the toolbar
commit; oh well. This moves the following text styles from being in
"experimental" mode to being regular annotations:

* Code
* Strikethrough
* Subscript
* Superscript
* Underline

Change-Id: I21be2dc844b47b825d7a1e48a592067166ecd122
(cherry picked from commit 1a1ef97336ba6d79cdc3e023aa51b05e45ea7373)