fix: typo in license-files (#1084)

Noticed in scikit-build/dynamic-metadata#39.

Author: henryiii

src/scikit_build_core/metadata/__init__.py

@@ -25,7 +25,7 @@
         "classifiers",
         "keywords",
         "dependencies",
-        "license_files",
+        "license-files",
     ]
 )