Increase height of logo

Summary: This increases the transparent space around the Phabricator logo. The logo itself is the same size. This allows for adding of other logos more easily without needing to alter the space provided. (Like Phacility)

Test Plan:
Reload page, screenshot logo, pull into Photoshop and verify spacing top and bottom.

{F309985}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11828