linux,macos: fix uv_set_process_title regression

The call to `uv__set_process_title()` had been accidentally removed.

Fixes: libuv#3037
PR-URL: libuv#3019
Refs: nodejs/node#35503
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: mmomtchev

src/unix/proctitle.c

@@ -119,6 +119,7 @@ int uv_set_process_title(const char* title) {
   memcpy(pt->str, title, len);
   memset(pt->str + len, '\0', pt->cap - len);
   pt->len = len;
+  uv__set_process_title(pt->str);
 
   uv_mutex_unlock(&process_title_mutex);