Safe fall distance attribute modifier for jump boost is not added when upgrading worlds

When upgrading a world from prior to 24w06a when the minecraft:generic.safe_fall_distance entity attribute, the attribute modifier added for jump boost is not added for players who already had jump boost. As a result, these players will incorrectly take damage from falls where they hadn't before.

Steps to reproduce

1. Create a 1.20.4 world
2. Give yourself the jump boost effect: /effect give @s jump_boost infinite 10
3. Observe that you do not take damage from simply jumping and falling
4. Load the world in 1.20.5 pre-release 1
5. Observe that you now take damage from simply jumping and falling

(This can be observed in vanilla with a standard jump boost potion, but the effect is less pronounced there.)