Fix comment for test_negotiated_group() test order

Fix comment for test_negotiated_group() test order

Because of how the 'client_multi' variable is set, we end up
running the tests where the client configures multiple groups (and
the server only configures one) before the ones where the server configures
multiple groups (and the client only configures one).

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16007)