[Doc] ssl_certificate_path config could be more clear

[andsel]

In the doc file https://github.com/logstash-plugins/logstash-integration-rabbitmq/blob/master/docs/input-rabbitmq.asciidoc#plugins-inputs-rabbitmq-ssl_certificate_path the definition for config variable ssl_certificate_path state that Path to an SSL certificate in PKCS12 (.p12) format used for verifying the remote host. On rough reading is not clear if it refer to server's certificate or client's one. Should be the client's certificate, because client ans server needs to do peer vaildation