Fix the RC4-MD5 cipher

A copy&paste error meant that the RC4-MD5 cipher (used in TLS) used the TLS
AAD data as the MAC key.

CVE-2022-1434

Fixes #18112

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
