build: Windows: bump Mingw-w64 from 8.1.0

[ee7]

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

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With the configlet 4.0.0-beta.1 release binary:

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

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Tracking issues for C compilers on the other platforms:

• https://github.com/exercism/configlet/issues/658
• https://github.com/exercism/configlet/issues/661