Change font size for edit links to small

As discussed on https://meta.wikimedia.org/wiki/Talk:Change_to_section_edit_links#Font_size

Followup to I6a6c12a9 / 7833589c.

Change-Id: I92b61ccb7291183a5beed1047d8e871afdc367ee
(cherry picked from commit 15543353f1b84738a8150a57718f4244a726e428)