util/mkdef.pl: use better array in search of 'DEPRECATEDIN_'

%disabled_algorithms isn't necessarily initialised with the "algos"
'DEPRECATEDIN_1_1_0' etc.  However, we know that @known_algorithms has
them all, so use that to find them instead.

Fixes #5157
(where this was reported)

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5282)