Update PyProject Toml - License

[robinjhuang]

Hey! Robin from comfy.org again 😊.

As a heads up, the license field is optional but in the case that it is filled out, the license file should be referenced either by the file path or by the name of the license.

• license = { file = "LICENSE" } ✅
• license = {text = "MIT License"} ✅
• license = "LICENSE" ❌
• license = "MIT LICENSE" ❌

This was brought up in our discord and so we're creating a small PR to update that optional field. For more info check out toml file standards or our docs page!