CI: Pin Windows SDK version to 10.0.22621.0

Author: kateinoigakukun

.github/workflows/main.yml

@@ -207,7 +207,7 @@ jobs:
       # - run: cmake -G Ninja -B .build/cmake
       # - run: cmake --build .build/cmake
       # Run tests with SwiftPM
-      - run: swift test
+      - run: swift test -Xswiftc -windows-sdk-version -Xswiftc 10.0.22621.0
 
   build-cmake:
     runs-on: ubuntu-20.04