Update Discussions-To to point to discourse thread

Author: di

pep-9999.rst

@@ -4,7 +4,7 @@ Version: $Revision$
 Last-Modified: $Date$
 Author: Dustin Ingram <[email protected]>
 BDFL-Delegate: Paul Moore <[email protected]>
-Discussions-To: Distutils SIG <distutils-sig@python.org>
+Discussions-To: https://discuss.python.org/t/the-next-manylinux-specification/
 Status: Active
 Type: Informational
 Content-Type: text/x-rst