[FIX]website: fix problem of hide snippet grid while it is on low resolu...

Task: https://www.odoo.com/web#id=10387&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.upol57weALe65Qfd
<b>Purpose of add <code>+</code> sign ?</b> : CSS <code>+</code> selector (also we can says sibling selector) that means this specified style applies only to  <code>.nav-margin-top</code> class element directly following to <code>#wrapwrap</code> id element.