Allays in pillager outposts spawn with half health

The bug

When first added, allays had 10 health and would spawn in pillager outposts. Their health was later increased to 20, but their old health was captured within the structure template pillager_outpost/feature_cage_with_allays.

Note that allays naturally regenerate their health, so this difference is only temporary.

Steps to reproduce

1. Join a world with commands enabled.

2. Run the following command:

   /place template minecraft:pillager_outpost/feature_cage_with_allays

3. Quickly run the following command:

   /data get entity @n[type=minecraft:allay] Health

4. Observe that the value of the Health tag is less than 20.