docs: Fixed typo

Fixed a clear copy/paste error, docs had said "call getHeight() to
get the width" when it should have been "...to get the height".

Skipping staging since it's a simple text change.

Change-Id: Ic06557ac38517f409943585054835d774240ccf3
Test: make ds-docs
Exempt-from-owner-approval: Docs-only change
Bug: 144537947