CSS: Make 'closed task links' grey color have more contrast
Summary:
Per https://we.phorge.it/D26393#38325, switch from `color: {$lightgreytext}` to `color: {$greytext}` for `a.handle-status-closed`.
Refs T15056
Test Plan:
* Go to http://phorge.localhost/settings/panel/display/ and set `Accessibility to Dark Mode (Experimental)`
* Create notifications, have setup issues, etc. Open top bar menu items and hover. Find a strike-through link, also hover
* Try the same in Default Mode
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: A_smart_kitten, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T15056
Differential Revision: https://we.phorge.it/D26503