Describe the bug
Skills that apply a visual effect to targets don't remove it once a skill has finished.

Steps to reproduce

1. Use an ability on a mob that applies a visual effect throughout the ability's duration (tested with Sap and Sleep)
2. Wait for the ability's expiration

Expected behavior
The visual effect should be removed from a target once the skill finishes its duration.

Screenshots
Dead creature with lingering Sap effect (which has sleep visual in 0.5.3)

Attacking creature with lingering sleep effect (which persisted once it woke up)