Replace SkinTemplateToolboxEnd hook with \SMW\BaseTemplateToolbox

[1] states "BaseTemplateToolbox also does the same thing, is cleaner and
more future proof than SkinTemplateToolboxEnd"

[1] https://www.mediawiki.org/wiki/Manual:Hooks/SkinTemplateToolboxEnd

Bug 45320

Change-Id: I4b3b7ed768479342e6a762d2dbacd3316fd510dd