build: Windows: bump Mingw-w64 from 8.1.0

Just a tracking issue. There's no extreme pressure to upgrade.

`windows-2022` currently uses `Mingw-w64 8.1.0`.

Links:
- https://github.com/actions/virtual-environments/blob/1e6e5cf82ee3/images/win/Windows2022-Readme.md
- https://www.mingw-w64.org/changelog/
- https://gcc.gnu.org/releases.html
- https://gcc.gnu.org/git/gcc.git
- https://community.chocolatey.org/packages/mingw#versionhistory
- https://scoopsearch.github.io/#/apps?q=gcc&o=true

---

With the configlet `4.0.0-beta.1` release binary:

```console
$ strings configlet.exe | grep gcc
GCC: (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0
```

---

Tracking issues for C compilers on the other platforms:
- https://github.com/exercism/configlet/issues/658
- https://github.com/exercism/configlet/issues/661