[MC-269801] Item display entities with a scale of 0 on the z-axis render darkened

Description

When an item display entity with scale: [X, Y, Z] and Z = 0.0f is summoned into the world, the entity is displayed as darkened (see example image), even when the light level around should make it appear bright. Setting brightness:{sky:15,block:15} has no effect on this behavior. This effect does not happen in version 1.20.4.

Steps to reproduce:

1. Summon a display entity with scale z=0:

/summon minecraft:item_display ~ ~5 ~ {item:{id:"minecraft:paper",count:1s},brightness:{sky:15,block:15},billboard:"fixed",interpolation_duration:0,start_interpolation:0, transformation: {left_rotation: [0.0f, 0.0f, 0.0f, 1.0f], translation: [0.0f, 0.0f, 0.0f], right_rotation: [0.0f, 0.0f, 0.0f, 1.0f], scale: [10.0f, 10.0f, 0.0f]}}

2. Summon another display entity with the same command, but set scale z=0.01 (or any other value):

/summon minecraft:item_display ~ ~5 ~ {item:{id:"minecraft:paper",count:1s},brightness:{sky:15,block:15},billboard:"fixed",interpolation_duration:0,start_interpolation:0, transformation: {left_rotation: [0.0f, 0.0f, 0.0f, 1.0f], translation: [0.0f, 0.0f, 0.0f], right_rotation: [0.0f, 0.0f, 0.0f, 1.0f], scale: [10.0f, 10.0f, 0.01f]}}