Remove the * {{msg}} syntax introduced to MediaWiki:Sidebar in r66974. This syntax...

Remove the * {{msg}} syntax introduced to MediaWiki:Sidebar in r66974. This syntax is in the way of projects attempting to use a more flexible sidebar-like message parser, or fixing the dependence on MediaWiki:Sidebar for sidebar config. Eliminating it before people end up using it in production (from my tests it never actually worked in 1.17).