Minor change for review - designing tips example

EOWG folks,

The following minor change is available for your review.

Was:
"Example: Design includes links to a transcript and to an alternative video"

Revised to:
"Example: Design includes links to a transcript and to an audio described video"

In context: <http://w3c.github.io/wai-quick-start/tips/designing/#include-image-and-media-alternatives-in-your-design>

If you have any comments on this change, you can add them to this GitHub issue: <https://github.com/w3c/wai-quick-start/pull/336>

Regards,
~Shawn, Sharron, Brent