BP Nouveau: in the Member's profile header, the avatar is box-shadowed by TwentySeventeen

[imath]

As a result: mention name, action buttons etc.. are over the avatar, see screencap below :

@hnla could you fix this ? It's probably also the case for the single Group's profile header..

[hnla]

In 12010:

Nouveau: Update item-header-content element

Commit adds padding to element to ensure it doesn't overlap the item avatar for desktop screens.

Props imath

Fixes #7778