Fix footer display when IconNav is present

Summary: Fixes T7382, specifically we were drawing double navs, removed those from each page and added the correct CSS rule.

Test Plan: Test a number of people and profile pages with a footer set.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7382

Differential Revision: https://secure.phabricator.com/D11895