Unused textures overridden in the material instance are still cooked

When creating a material and then overriding the textures on the new material instance, the unused textures are still included in the cooking process.

1. Create a blank project with starter content
2. Create a material instance from a material
3. Override the texture within the material instance
4. Save the project
5. Cook the project and review the logs

Expected: The unused materials shouldn't appear within the cooking logs.
Results: The unused material is in the cooking logs, along with the updated texture for the material instance.