Remove dead code

* Remove .jshintrc
  Unused, there are no JavaScript files here anymore.

* Remove unused $vectorResourceTemplate toplevel variable

* Remove 'vector-collapsiblenav-preference' message
  Unused as of I47950b53.

* Remove 'vector-simplesearch-search', 'vector-simplesearch-containing' messages
  Previously removed in Ib8ebba17, apparently erreneously restored by
  Translation updater bot in I89923f52

* Remove BeforePageDisplay, ResourceLoaderGetConfigVars, GetPreferences hooks
  No longer do anything, as all of the features have been removed.

* Remove MakeGlobalVariablesScript hook, VectorHooks::isEnabled method
  No longer do anything per above, global $wgVectorFeatures which they
  refer to no longer exists (removed in I47950b53).

* Remove default true value for 'vector-simplesearch' preference
  The preference (with the default value) was added in Vector in r68177,
  moved to core in r68224. Default moved to core in Id5e96f5e.

Bug: 45051
Change-Id: If24b0055a94ae254f8f5c639c3f02507d17402a8