C API discussions now go to Discourse

Retirement notice: https://mail.python.org/archives/list/capi-sig@python.org/thread/NXB3D56VHECOCU7U2LVS2UF36PWZIO3E/

Author: hugovk

developer-workflow/c-api.rst

@@ -395,9 +395,8 @@ If following these guidelines would hurt performance, add a fast function
 API.
 
 If anything is unclear, or you have a good reason to break the guidelines,
-consider discussing the change at the `capi-sig`_ mailing list.
-
-.. _capi-sig: https://mail.python.org/mailman3/lists/capi-sig.python.org/
+consider discussing the change in the `C API category
+<https://discuss.python.org/c/core-dev/c-api/>`__ on Discourse.
 
 Adding a new definition to the Limited API
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