Power cell overlay now updates when exiting an object's contents (#85079)

## About The Pull Request
The charge indicator overlay on power cells is now properly updated when
the cell is charged/discharged. Before, you could use a power cell until
it's empty and the overlay wouldn't change at all.
## Why It's Good For The Game
The overlay is there to indicate the charge of the cell. It should work.
## Changelog
🆑
fix: The charge indicators on power cells now work properly.
code: Removed some now redundant power cell appearance updates
/🆑

---------

Co-authored-by: jimmyl <70376633+mc-oofert@users.noreply.github.com>

code/modules/mod/mod_core.dm

@@ -173,7 +173,6 @@
 /obj/item/mod/core/standard/proc/uninstall_cell()
 	if(!cell)
 		return
-	cell.update_appearance()
 	cell = null
 	mod.update_charge_alert()