Remove ENGINE_load_dasync() (no OPENSSL_INIT_ENGINE_DASYNC already)

Fixes: 8d00e30f

 ("Don't try to init
dasync internally")

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
CLA: trivial
(cherry picked from commit b9b5181d)