The previous commit declared that some tests cases in ssl-opt.sh depend
on USE_PSA being disabled, which is the right thing to do.
We had a check that forbade that - it was mainly meant to prevent
accidental re-introduction of such dependencies after we cleaned up a
number of cases where it was not warranted, but already at the time that
was controversial [1]. Now it's preventing us from doing the right
thing, so let's just remove it.
[1]: https://github.com/Mbed-TLS/mbedtls/pull/5742#discussion_r855112412
See also https://github.com/Mbed-TLS/mbedtls/pull/5907/ which also
removes this for a similar reason.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>