curl_multi_init: fix return description (#2591)

ref.: https://github.com/php/php-src/blob/master/ext/curl/multi.c#L60 (stub: `function curl_multi_init(): CurlMultiHandle {}`)

Author: voku

reference/curl/functions/curl-multi-init.xml

@@ -25,7 +25,7 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   Returns a cURL multi handle on success, &false; on failure.
+   Returns a cURL multi handle.
   </para>
  </refsect1>