[PHPDoc] Fix some union type cases

Author: fancyweb

ResponseInterface.php

@@ -97,15 +97,15 @@ public function cancel(): void;
      *  - response_headers (array) - an array modelled after the special $http_response_header variable
      *  - start_time (float) - the time when the request was sent or 0.0 when it's pending
      *  - url (string) - the last effective URL of the request
-     *  - user_data (mixed|null) - the value of the "user_data" request option, null if not set
+     *  - user_data (mixed) - the value of the "user_data" request option, null if not set
      *
      * When the "capture_peer_cert_chain" option is true, the "peer_certificate_chain"
      * attribute SHOULD list the peer certificates as an array of OpenSSL X.509 resources.
      *
      * Other info SHOULD be named after curl_getinfo()'s associative return value.
      *
-     * @return array|mixed|null An array of all available info, or one of them when $type is
-     *                          provided, or null when an unsupported type is requested
+     * @return array|mixed An array of all available info, or one of them when $type is
+     *                     provided, or null when an unsupported type is requested
      */
     public function getInfo(string $type = null);
 }