lhash_test: set back num_workers to 16

lhash_test: set back num_workers to 16

commit 131c2a1adba1 ("Defang the lhash test") has reduced default number
of the thread workers in CI to HARNESS_JOBS / 4. Setting LHASH_WORKERS
will set it back.

Resolves: https://github.com/openssl/project/issues/1769
Signed-off-by: Nikola Pajkovsky <nikolap@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
MergeDate: Mon Jan 12 10:09:54 2026
(Merged from https://github.com/openssl/openssl/pull/29565)