Revert "CI,TST: Run sdist tests on all platforms."

This reverts commit a3f05cd.

Can't use mkdir and cd in CI with windows."

Author: rossbar

.github/workflows/test.yml

@@ -187,7 +187,7 @@ jobs:
     runs-on: ${{ matrix.os }}-latest
     strategy:
       matrix:
-        os: [ubuntu, macos, windows]
+        os: [ubuntu]
         python-version: ["3.14"]
     steps:
       - uses: actions/checkout@v5