Address Coverity 1493362 resource leak

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16962)

(cherry picked from commit 1b4d9967a2)

providers/implementations/keymgmt/mac_legacy_kmgmt.c

@@ -508,6 +508,7 @@ static void *mac_gen(void *genctx, OSSL_CALLBACK *cb, void *cbarg)
      * of this can be removed and we will only support the EVP_KDF APIs.
      */
     if (!ossl_prov_cipher_copy(&key->cipher, &gctx->cipher)) {
+        ossl_mac_key_free(key);
         ERR_raise(ERR_LIB_PROV, ERR_R_INTERNAL_ERROR);
         return NULL;
     }