fix build with gcc-15 and -Werror=unterminated-string-initialization

Author: niol

core/init.c

@@ -3,7 +3,7 @@
 extern struct uwsgi_server uwsgi;
 
 struct http_status_codes {
-        const char      key[3];
+        const char      key[4];
         const char      *message;
         int             message_size;
 };