fips: Unblock MD5 in fips mode but mark non-approved in indicator.

* cipher/mac-hmac.c (_gcry_mac_type_spec_hmac_md5): Allow in fips mode.
* cipher/md5.c (_gcry_digest_spec_md5): Allow in fips mode.

• GnuPG-bug-id: T6376
• Signed-off-by: Tobias Heider <tobias.heider@canonical.com>