Leash all frog variants advancement is not deterministic in data generation

Frog variants are now data-driven, meaning there isn't a defined order to the registry. Since the leash all frog variants uses this registry to determine its requirements, the requirements may end up in any order, which is non-deterministic behavior.

An example of the non-determinism can be seen in the file history for this advancement: https://github.com/misode/mcmeta/blob/e7020ccbc13e72ccaf901c71621ce35cb366a83b/data/minecraft/advancement/husbandry/leash_all_frog_variants.json

Previous data generation determinism issues have been considered valid.