R1:cd99850cb8db

Increase Maniphest auxiliary storage size.

Test Plan:
Store large amounts of text into a string auxiliary field. It should
be stored successfully rather than truncated.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2575

Differential Revision: https://secure.phabricator.com/D5246