http_async_client: fix warning deprecated-non-prototype

> Warning: ./http_multi.h:64:5: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C23, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
>    64 | int init_http_multi();
>       |     ^
> http_multi.c:403:5: note: conflicting prototype is here
>   403 | int init_http_multi(struct event_base *evbase, struct http_m_global *wg)
>       |     ^
> 1 warning generated.

(cherry picked from commit 2737bb19a363be7c0d67749b75f11c7e9d2d09f3)

src/modules/http_async_client/http_multi.h

@@ -61,7 +61,7 @@ extern int curl_verbose;
 extern int curl_follow_redirect;
 
 void set_curl_mem_callbacks(void);
-int init_http_multi();
+int init_http_multi(struct event_base *evbase, struct http_m_global *wg);
 int multi_timer_cb(CURLM *multi, long timeout_ms, struct http_m_global *g);
 void timer_cb(int fd, short kind, void *userp);
 int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp);