getaddrinfo.3: Use sizeof consistently

Use ``sizeof`` consistently through all the examples in the following
way:

- Use the name of the variable instead of its type as argument for
  ``sizeof``.

	Rationale:
	https://www.kernel.org/doc/html/v5.8/process/coding-style.html#allocating-memory

Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/getaddrinfo.3

@@ -721,7 +721,7 @@ main(int argc, char *argv[])
     /* Read datagrams and echo them back to sender */
 
     for (;;) {
-        peer_addr_len = sizeof(struct sockaddr_storage);
+        peer_addr_len = sizeof(peer_addr);
         nread = recvfrom(sfd, buf, BUF_SIZE, 0,
                 (struct sockaddr *) &peer_addr, &peer_addr_len);
         if (nread == \-1)