Fix bug in Citus maintenance daemon initialization

In maintenanced.c:

> L216 is doing a strcpy_s() into bgw_function_name, but using sizeof(bgw_library_name).

```c
/* Restart after a bit after errors, but don't bog the system. */
worker.bgw_restart_time = 5;
strcpy_s(worker.bgw_library_name,
sizeof(worker.bgw_library_name), "citus");
strcpy_s(worker.bgw_function_name, sizeof(worker.bgw_library_name),
"CitusMaintenanceDaemonMain");
```