Update setup.cfg to `description_file` field (#7248)

Resolve `UserWarning: Usage of dash-separated 'description-file' will not be supported in future versions. Please use the underscore name 'description_file' instead`

Update setup.cfg to `description_file` field (#7248)
6f4eb95a · Glenn Jocher · GitHub · a19406b3 · 6f4eb95a
--- a/setup.cfg
+++ b/setup.cfg
@@ -4,7 +4,7 @@
 [metadata]
 license_file = LICENSE
-description-file = README.md
+description_file = README.md
 [tool:pytest]