R1:6825e6ca77d5

Soften shadow on white icons

Summary: The shadow on the white icons was too harsh for their size, looked bad on timelines.

Test Plan: Check timeline example, phuilist example.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D6176