chore: fix pyproject.toml SIPv7 compat

Author: 3np

pyproject.toml

@@ -8,7 +8,7 @@ version = "0.9.12dev"
 description = "Joinmarket client library for Bitcoin coinjoins"
 readme = "README.md"
 requires-python = ">=3.8,<3.13"
-license = {file = "LICENSE"}
+license-files = ["LICENSE"]
 dependencies = [
     "chromalog==1.0.5",
     "cryptography==42.0.4",