PEP 3156: Fix a typo — "ipv4_address" -> "ipv6_address" (#3721)

Typo fix.

Author: ryomahan

peps/pep-3156.rst

@@ -564,7 +564,7 @@ usually called implicitly by ``create_connection()``,
   format as returned by ``socket.getaddrinfo()``, i.e. a list of
   ``(address_family, socket_type, socket_protocol, canonical_name,
   address)`` where ``address`` is a 2-tuple ``(ipv4_address, port)``
-  for IPv4 addresses and a 4-tuple ``(ipv4_address, port, flow_info,
+  for IPv4 addresses and a 4-tuple ``(ipv6_address, port, flow_info,
   scope_id)`` for IPv6 addresses.  If the ``family`` argument is zero
   or unspecified, the list returned may contain a mixture of IPv4 and
   IPv6 addresses; otherwise the addresses returned are constrained by