The table of sys.flags doesn't have warn_default_encoding attribute.

https://docs.python.org/3/library/sys.html?highlight=sys%20flags#sys.flags

PEP 597 – Add optional EncodingWarning https://peps.python.org/pep-0597/

![image](https://github.com/python/cpython/assets/114795525/1d8c8b8c-88bd-4809-b71c-f3f2e4ec4709)



### Linked PRs
* gh-106854
* gh-106958
* gh-107054