[MC-259775] Mobs don't swap their armour for better armour

Mobs (with CanPickUpLoot set to 1b) don't swap out their armour for better ones.

Steps to Reproduce:
1) Run

/summon zombie ~ ~ ~ {CanPickUpLoot:1b}

2) Drop an iron helmet and wait for it to wear it
3) Drop a netherite helmet and note that the armour isn't swapped

Linked issues

Thank you for your report!
We're tracking this issue in MC-259259, so this ticket is being resolved and linked as a duplicate.

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