update dox for vertical-text demise

Bug: skia:
Change-Id: I0c8887fc31ea491a155ce9f182bbd5235f403120
Reviewed-on: https://skia-review.googlesource.com/c/164607
Commit-Queue: Mike Reed <reed@google.com>
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>
Auto-Submit: Mike Reed <reed@google.com>
2 files changed