fix: not compiling against curl 8.16.0

Including curl/multi.h now requires including curl/curl.h before.

This is alreay fixed by curl_prelude.h, so just include that instead of
manually including curl multi.

Author: steve-chavez

src/event.h

@@ -1,7 +1,7 @@
 #ifndef EVENT_H
 #define EVENT_H
 
-#include <curl/multi.h>
+#include "curl_prelude.h"
 
 #include "core.h"