Multiple `mismatched-new-delete` warnings with gcc 11.3 and -Wall

When building latest master (`53fded2`) with gcc 11.3 (Ubuntu 22.04) and `-Wall`, the compiler complains about mismatched new-delete warnings. See snippet below:

```
/home/jfp/async/test/async_for.cpp: In function ‘boost::async::generator test_data_gen()’:
/home/jfp/async/test/async_for.cpp:30:1: warning: ‘static void boost::async::promise_memory_resource_base::operator delete(void*, std::size_t)’ called on pointer returned from a mismatched allocation function [-Wmismatched-new-delete]
30 | }
```

Is this warning safe to ignore?