Fixed "update inventory X" procs and clothes from wizarditis not showing

#### In this pull request:

* The ["clothes from wizarditis not showing" bug](https://github.com/tgstation/-tg-station/issues/3235) was a leftover : the items (Wizard's hat, robe and sandals) were manually created and the HUD never updated. The items were thus present but invisible in the inventory. Unequipping/equipping them would update the HUD, making them appear again.

The fix was to call the right proc (equip to slot or del), that correctly handles updating the HUD .

*File changed :  code/datums/diseases/wizarditis.dm*

* Investigating the wizarditis bug, i found that the "update inv X" procs were bugged in that the inventory HUD was not updated if the inventory panel was closed (technically, the items were not added to the client.screen).

An item could then appears invisible in the inventory panel if forced equipped while the inventory panel was closed.
These procs are fixed to update the inventory HUD even if the panel is closed.

*File changed : code/modules/mob/living/carbon/human/update_icons.dm*

**Both changes have been tested and are working.**