Drop explicit check for engines in opt_legacy_okay

Drop explicit check for engines in opt_legacy_okay

The providers indication should always indicate that this is not a
legacy request.
This makes a check for engines redundant as the default return is that
legacy is ok if there are no explicit providers.

Fixes #19662

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19671)

(cherry picked from commit 2fea56832780248af2aba2e4433ece2d18428515)