Fix double-bordered breadcrumbs in Phame blogs

Summary: Ref T13661. The Phame blog main page has a double breadcrumb border in non-live mode.

Test Plan: Viewed a blog page in internal and live modes, saw single border in both cases (previously: double border for internal mode).

Maniphest Tasks: T13661

Differential Revision: https://secure.phabricator.com/D21750