Temporary hax to hide cawiki's hacked in search sidebar

Temporary hax to hide cawiki's hacked in search sidebar

For the sistersearch AB test we will be adding in interwiki results. For
this to work we need to hide the sidebar that cawiki hacked into place
via the searchmenu-new i18n message. This should only be temporary, on
a full rollout the i18n message will be fixed, but for the AB test we
need to leave the sidebar in place for everyone not in the test.

This CSS is only delivered to pages that render the new interwiki
sidebar of results and wont negatively effect users outside the test.

Bug: T149806
Change-Id: I0c86b51222d7ecb68c72c45649e102d8c5589dea