Stop long filenames in objective list tooltips from being cut off

Summary: Ref T12733. Currently, long filenames get cut off at 160px. Instead, don't cut them off.

Test Plan:
Before:

{F4968401}

After:

{F4968402}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12733

Differential Revision: https://secure.phabricator.com/D17975