fix(tokens): Update Access Token Validation Logic to only update token when expiry_date changes

This MR updates the logic for ModifyPlan in several token resources to ensure that the new validation logic only happens when the expiry_date is changing, instead of having changes when the validation boolean changes. We'll likely want to revert this in 19.0, since it prevents people from changing the validation boolean without rotating the token, but it's OK for now.

Closes #6642 (closed)