json: fix array element deletion

OpenSIPS incorrectly calls the JSON-C array element deletion function by passing the size of the array instead of the desired count of elements to delete. When attempting to delete from index `0`, it results in the deletion of all elements, while specifying an index greater than `0` leads to no deletion due to overindexing.

### Example 1:
```
  $json(obj) := "[ 1, 2, 3 ]";
  $json(obj[0]) = NULL;
  xlog("$json(obj)\n");
```
Result:   `[]`
Expected: `[ 2, 3 ]`

### Example 2:
```
  $json(obj) := "[ 1, 2, 3 ]";
  $json(obj[1]) = NULL;
  xlog("$json(obj)\n");
```
Result:   `[ 1, 2, 3 ]`
Expected: `[ 1, 3 ]`

modules/json/array_del.c

@@ -31,8 +31,7 @@
 void json_object_array_del(struct json_object* obj, int idx)
 {
 #if JSON_C_VERSION_NUM >= JSON_C_VERSION_013
-	array_list_del_idx(json_object_get_array(obj), idx,
-		json_object_get_array(obj)->length);
+	array_list_del_idx(json_object_get_array(obj), idx, 1);
 #else
 	if(idx >= obj->o.c_array->length)
 		return;