Losing health_boost effect heals player to 20HP

The bug

When you lose the health boost effect, your health replenishes to 20 health points.

How to reproduce

1. Get the health boost effect (/effect @s health_boost 60 3)
2. Take damage until you have less than 20 HP
3. Drink milk or wait until the health boost effect runs out

Observed Result: When you have less than 20 HP and then you lose the health boost effect you are fully healed to 20 HP.

Expected Result: Your health should remain the same after the effect is lost.