ndb_redis: docs - refine docs regarding client certificates [skip ci]

The created ssl context does not use client certificates [1,2] which is against the default in current Redis configurations [3]. The used Redis server therefore needs to be configured to not use tls-auth-clients [3].

There is also a small typo in "ac_path" which was fixed to "ca_path".

[1]: https://github.com/kamailio/kamailio/blob/8047c958b42ea5af2e8f9ede0152f892ac0eea3a/src/modules/db_redis/redis_connection.c#L168
[2]: https://github.com/kamailio/kamailio/blob/8047c958b42ea5af2e8f9ede0152f892ac0eea3a/src/modules/db_redis/redis_connection.c#L212
[3]: https://redis.io/docs/management/security/encryption/#client-certificate-authentication

src/modules/ndb_redis/doc/ndb_redis_admin.xml

@@ -75,6 +75,12 @@
 			many REDIS servers, just give different attributes and use the specific
 			server name when querying the REDIS instance.
 		</para>
+		<para>
+			If tls is enabled, the module will validate the REDIS server certificate against the
+			ca_path. There is currently no way to connect with a specified client certificate, the
+			<ulink url="https://redis.io/docs/management/security/encryption/#client-certificate-authentication">corresponding configuration</ulink>
+			to check client certificates in the REDIS server must therefore be turned off.
+		</para>
 		<para>
 		<emphasis>
 			Default value is NULL.
@@ -330,9 +336,9 @@ modparam("ndb_redis", "debug", 1)
 		</example>
 	</section>
 	<section id="ndb_redis.p.ca_path">
-		<title><varname>ac_path</varname> (string)</title>
+		<title><varname>ca_path</varname> (string)</title>
 		<para>
-			Sets the path where Certificates Authorities certs are stored.
+			Sets the path where Certificates Authorities certs for the REDIS server certificate are stored.
 		</para>
 		<para>
 			Default value: "" (empty).