docs: Restore "docs: Added 3-month and 6-month subscription periods"

See first comment for doc stage location.

This restores commit 29b498bb157fda1c2d7c70510c417a1817959776 , which
had been submitted prematurely, and was reverted by
commit 5c83c761064ddd44c01baeff8d17468c5063d845

bug: 24168299

Change-Id: Ib941b459c99581217df7b5438fb1b06686e5be7d
1 file changed