Use text, not icons, to indicate content sources

Summary:
oh god everyone hates this

revert revert

https://www.facebook.com/photo.php?fbid=787360256660&set=p.787360256660&type=1&theater

(I left the icons themselves since I have some plans to do other things with
them.)

Test Plan: I am not good at designer

Reviewers: ola, elynde, bh, ashwin, jungejason, kdelong, zrait, tomo, aran

Reviewed By: aran

CC: aran, epriestley, tomo

Differential Revision: 885