ref: license_file is deprecated (#65240)

<!-- Describe your PR here. -->

setup.cfg

@@ -8,7 +8,7 @@ url = https://sentry.io
 author = Sentry
 author_email = oss@sentry.io
 license = FSL-1.0-Apache-2.0
-license_file = LICENSE.md
+license_files = LICENSE.md
 classifiers =
     Framework :: Django
     Intended Audience :: Developers