Fix margins after they were broken in 9d988924

Changes in MediaWiki core to the padding of div#content in Vector
(see 9d988924a0350228745375e074420a0e1214f7e3 ) made the toolbar in
VisualEditor's ViewPageTarget integration for Vector render incorrectly.

This adjusts the toolbar margins to match the changes in content padding.

Bug: 61224
Change-Id: Ie6b47f5d1929533669118ba51202c1fccda4a0d6
Merge "Fix margins after they were broken in 9d988924"