Revert "wmllint: ids in [time_area] are not associated to units most of the time"

Done already in r55047 by anonymissimus.

This reverts commit r56343.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56345 75b3775d-3801-0410-9e12-e2e43121521d