Remove documentation about emboss.

BUG=skia:

NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=5708

Change-Id: Iac133df3778061509f5754aa6a742cebc2ab6ba6
Reviewed-on: https://skia-review.googlesource.com/5708
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Heather Miller <hcm@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
2 files changed