Remove a reference to SSL_force_post_handshake_auth()

That function was removed in favour of SSL_set_post_handshake_auth().
Update the docs accordingly.
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7139)

doc/man3/SSL_CTX_set_verify.pod

@@ -186,7 +186,7 @@ Its return value is identical to B<preverify_ok>, so that any verification
 failure will lead to a termination of the TLS/SSL handshake with an
 alert message, if SSL_VERIFY_PEER is set.
 
-After calling SSL_force_post_handshake_auth(), the client will need to add a
+After calling SSL_set_post_handshake_auth(), the client will need to add a
 certificate or certificate callback to its configuration before it can
 successfully authenticate. This must be called before SSL_connect().