Semi-transparent pixels on axolotl textures

Some pixels on the axolotl textures are not fully opaque.

Affects:

• 'axolotl_lucy'
• 'axolotl_gold'
• 'axolotl_cyan'
• 'axolotl_blue'

Does not affect:

• 'axolotl_wild'

Images:

• 'axolotl_lucy' texture with translucent pixels on fin, tail, and gills.
• 'axolotl_cyan' texture with translucent pixels on fin, tail, and gills.
• Cyan Axolotl in-game; pixels don't appear transparent at all.