Deprecate duplicated gliding boost method

[imDaniX]

Is your feature request related to a problem?

Currently there's two almost identical methods for giving player a boost while gliding:
Spigot's HumanEntity#fireworkBoost(ItemStack)
Paper's Player#boostElytra(ItemStack)

Describe the solution you'd like.

Deprecate one of those in favor of other.

Describe alternatives you've considered.

Well, I can just ignore one of those I guess.

Other

No response

[Machine-Maker]

They do have a slightly different implementation. Paper's #boostElytra has a precondition that they #isGliding method returns true. Spigot's has no such check. So which one should be deprecated partially depends on which is more "correct".