Including pep658 in the simple API description (#1061)

* Included pep658 in the simple API description

* bhrutledge update source/specifications/simple-repository-api.rst

Co-authored-by: Brian Rutledge <brian@bhrutledge.com>

Co-authored-by: Brian Rutledge <brian@bhrutledge.com>

Author: Wouterkoorn

source/specifications/simple-repository-api.rst

@@ -8,5 +8,6 @@ Simple repository API
 The current interface for querying available package versions and
 retrieving packages from an index server is defined in :pep:`503`,
 with the addition of "yank" support (allowing a kind of file deletion)
-as defined in :pep:`592` and specifying the interface version provided
-by an index server in :pep:`629`.
+in :pep:`592`, specifying the interface version provided
+by an index server in :pep:`629`, and providing package metadata 
+independently from a package in :pep:`658`.