Warden's ranged attack is affected by the game's diffculty

Related issue: MC-250948

There's a same description in 22w17a's and 1.19.0.28's changelog:

"Deals 10 damage instead of 30 damage"

But, different with the Java Edition, the damage in the Bedrock Edition is affected by difficulty. So, the actual damage is 6 for easy, 10 for normal, and 15 for hard, rather than 10 for every difficulty in Java Edition.

Steps to reproduce:

1. Switch the difficulty to easy / normal / hard respectively.
2. Let the warden cast a ranged attack. (e.g: build a pillar, and throw snowballs on it)
3. See the difference on the health bar.