shulker_boxes atlas includes the shulker bullet texture

Relates to MC-276566.

The bug

The way that the shulker_boxes atlas is defined causes it to include the texture for the shulker bullet. However, as this atlas is only used for rendering shulker boxes, and not shulkers or their projectiles, this inclusion is effectively pointless.

How to reproduce

A resource pack that unloads the entire shulker boxes atlas is included in this ticket.

1. Apply this resource pack
2. Look at a shulker bullet

Expected results

If the bullet texture is included in this atlas for a reason, then having the atlas unloaded would cause it to use a missing texture.

Actual results

It still has a texture, indicating that the bullet texture is being included erroneously.

How to fix

Very simple to fix - simply add the following to the atlas file for shulker boxes:

,
    {
      "type": "filter",
      "pattern": {
        "path": "spark"
	  }
    }

I've attached a resource pack that fixes this issue to this ticket.

Note that restarting the game is required after applying this resource pack if you intend to use F3+S to print the atlas textures to disk, due to MC-263119, otherwise the bullet texture may remain.