Fixes a stray pixel in the warrior 'walking' sprite. (#5590)

# About the pull request

Fixes a stray pixel in the warrior 'walking' sprite. (Also the sleeping
icon state for the boxer strain, but that isn't currently used.)

# Explain why it's good for the game

Weird floaty white pixels.

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

**Before:**

![before](https://github.com/cmss13-devs/cmss13/assets/57483089/0d06ec1a-1faf-4f32-a5b2-9cd2844f55b7)

**After:**

![after](https://github.com/cmss13-devs/cmss13/assets/57483089/bcd4ae66-9a95-46aa-917a-5697d96ab59b)

</details>


# Changelog
:cl:
fix: Fixed a stray pixel in the warrior 'walking' sprite.
/:cl: