Remove hyphenated variables in setup.cfg (vmware#1148)

Signed-off-by: Aniruddha Shamasundar <aniruddha.9794@gmail.com>

setup.cfg

@@ -5,8 +5,8 @@
 [metadata]
 name = container-service-extension
 summary = Container Service Extension for vCloud Director
-description-file =
-    README.md
+long_description = file: README.md
+long_description_content_type = text/markdown
 author = Paco Gomez
 author_email = pgomez@vmware.com
 url = https://github.com/vmware/container-service-extension
@@ -22,7 +22,7 @@ classifier =
     Programming Language :: Python
     Programming Language :: Python :: 3
 
-requires-python = >=3
+python_requires = >= 3.7
 
 [entry_points]
 console_scripts =