[MC-109844] en_us.json contains unused strings

"selectWorld.empty": "empty"
"selectServer.empty": "empty"
"stat.blocksButton": "Blocks"
"item.leaves.name": "Leaves"
"item.minecraft.skeleton_skull": "Skeleton Skull"
"item.minecraft.wither_skeleton_skull": "Wither Skeleton Skull"
"item.minecraft.zombie_head": "Zombie Head"
"item.minecraft.creeper_head": "Creeper Head"
"item.minecraft.dragon_head": "Dragon Head"
"block.minecraft.flowing_lava": "Flowing Lava"
"block.minecraft.flowing_water": "Flowing Water"
"block.minecraft.four_turtle_eggs": "Four Turtle Eggs"
"block.minecraft.three_turtle_eggs": "Three Turtle Eggs"
"block.minecraft.two_turtle_eggs": "Two Turtle Eggs"
"block.minecraft.banner": "Banner"
"block.minecraft.wall_banner": "Wall Banner"
"block.minecraft.bed": "Bed"
"translation.test.none": "Hello, world!"
"translation.test.complex": "Prefix, %s%2$s again %s and %1$s lastly %s and also %1$s again!"
"translation.test.escape": "%%s %%%s %%%%s %%%%%s"
"translation.test.invalid": "hi %"
"translation.test.invalid2": "hi %  s"
"translation.test.args": "%s %s"
"translation.test.world": "world"

These aren't used anywhere:

selectWorld/selectServer.empty there's no empty option, and I couldn't find any other way to trigger this message
the statics screen no longer has a blocks option, as it got merged with items
leaves uses separate block translation strings
skulls/head use the block strings
flowing liquid blocks got removed
there's only 1 translation string per block; and any count of turtle eggs is minecraft:turtle_egg
(wall_)banner was added in the flattening, but never used
beds use separate strings since the flattening
translation.test was only for the initial translation tests, and is not used anymore