docs: Update page description endpoints
docs: Update page description endpoints

Following patch 635017, this patch updates the docs to include
the ability to write to short descriptions on wikis that use
local descriptions.

Bug: T264024
Change-Id: I74b11358c3332f4760fd12c8277a8b0cd23d4421

wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps