Temporarily don't install WSL system to test xfail

This reverts "Install WSL system on CI for hook tests",
commit 7663d9d.

Assuming both cases are found to be working, the removed step will
either be brought back or replaced with a very similar step that
installs a different distribution.

.github/workflows/pythonpackage.yml

@@ -35,12 +35,6 @@ jobs:
         python-version: ${{ matrix.python-version }}
         allow-prereleases: ${{ matrix.experimental }}
 
-    - name: Set up WSL
-      if: startsWith(matrix.os, 'windows')
-      uses: Vampire/setup-wsl@v2.0.2
-      with:
-        distribution: Debian
-
     - name: Prepare this repo for tests
       run: |
         ./init-tests-after-clone.sh