Fix a copy&paste error in the TLSv1.3 server side PSK documentation

The introductory paragraph for the TLSv1.3 server side PSK documentation
is a copy & paste of the client side documentation which has not been
updated with the server side equivalent information.
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10245)

(cherry picked from commit c549cb46e0d3cb4e611acafae5f919b4a8df4007)

doc/man3/SSL_CTX_use_psk_identity_hint.pod

@@ -39,9 +39,9 @@ SSL_set_psk_find_session_callback
 
 =head1 DESCRIPTION
 
-A client application wishing to use TLSv1.3 PSKs should set a callback
-using either SSL_CTX_set_psk_use_session_callback() or
-SSL_set_psk_use_session_callback() as appropriate.
+A server application wishing to use TLSv1.3 PSKs should set a callback
+using either SSL_CTX_set_psk_find_session_callback() or
+SSL_set_psk_find_session_callback() as appropriate.
 
 The callback function is given a pointer to the SSL connection in B<ssl> and
 an identity in B<identity> of length B<identity_len>. The callback function