Update peps/pep-0759.rst

Co-authored-by: Ethan Smith <[email protected]>

peps/pep-0759.rst

@@ -427,7 +427,7 @@ Several ideas were considered and rejected.
   the benefit is not likely worth the additional complexity.
 - Periodic verification of the download URLs by the index. PyPI could try to periodically
   ensure that the external wheel host or the external ``.whl`` file itself is still
-  available, e.g. via an ``HTTP HEAD`` request. This is likely overkill and without also
+  available, e.g. via an :rfc:`9110#section-9.3.2` request. This is likely overkill and without also
   providing the file's checksum in the response [#fn2]_, may not provide much additional
   benefit.
 - This PEP could allow for an organization to provide fallback download hosts,