test/evp_test.c: Free fetched_digest on error to avoid memory leak

test/evp_test.c: Free fetched_digest on error to avoid memory leak

Call EVP_MD_free() to release fetched_digest if OPENSSL_zalloc() fails, preventing a memory leak.

Fixes: 2208ba56eb ("evp_test: Add the missing check after calling OPENSSL_malloc")
Signed-off-by: JiashengJiang <jiasheng@purdue.edu>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27648)

(cherry picked from commit e8deb32af4874c781838c1596c6355712b5d0ed0)