Use license_files instead of license_file setup.cfg

See pypa/setuptools#2620

setup.cfg

@@ -5,7 +5,7 @@ author = Tür an Tür – Digitalfabrik gGmbH
 author_email = [email protected]
 description = Content Management System for the Integreat App
 url = https://integreat-app.de/en/
-project_urls = 
+project_urls =
 	Funding=https://integreat-app.de/en/donation/
 	Documentation=https://digitalfabrik.github.io/integreat-cms/
 	Issues=https://github.com/digitalfabrik/integreat-cms/issues
@@ -14,8 +14,8 @@ project_urls =
 long_description = file: README.md
 long_description_content_type = text/markdown
 license = Apache License 2.0
-license_file = LICENSE.txt
-classifiers = 
+license_files = LICENSE.txt
+classifiers =
 	Development Status :: 4 - Beta
 	License :: OSI Approved :: Apache Software License
 	Operating System :: OS Independent
@@ -29,7 +29,7 @@ classifiers =
 	Topic :: Internet :: WWW/HTTP :: WSGI :: Application
 	Natural Language :: English
 	Natural Language :: German
-keywords = 
+keywords =
 	integreat
 	cms
 	django
@@ -40,7 +40,7 @@ keywords =
 
 [options]
 packages = find:
-install_requires = 
+install_requires =
 	aiohttp
 	argon2-cffi
 	bcrypt
@@ -76,7 +76,7 @@ scripts = integreat_cms/integreat-cms-cli
 [bumpver]
 current_version = 2022.6.3
 version_pattern = YYYY.MM.INC0[-TAG]
-commit_message = 
+commit_message =
 	Bump version to {new_version}
 	[skip ci]
 commit = True