[3.11] Add IPv6 into to the docstring for socket.getsockname (GH-102961) (#103137)

Add IPv6 into to the docstring for socket.getsockname (GH-102961)
(cherry picked from commit ecc5441)

Signed-off-by: Brian Haley <haleyb.dev@gmail.com>
Co-authored-by: Brian Haley <brianphaley@gmail.com>

Author: miss-islington

Modules/socketmodule.c

@@ -3411,7 +3411,8 @@ PyDoc_STRVAR(getsockname_doc,
 \n\
 Return the address of the local endpoint. The format depends on the\n\
 address family. For IPv4 sockets, the address info is a pair\n\
-(hostaddr, port).");
+(hostaddr, port). For IPv6 sockets, the address info is a 4-tuple\n\
+(hostaddr, port, flowinfo, scope_id).");
 #endif