Revert "mach: switch to uv for managing python venv (#34504)" (#34548)

This reverts commit 4103421ba5.

Signed-off-by: Mukilan Thiyagarajan <mukilan@igalia.com>

.github/workflows/mac-wpt.yml

@@ -41,11 +41,15 @@ jobs:
       - uses: actions/download-artifact@v4
         with:
           name: ${{ inputs.profile }}-binary-macos
-      - name: Setup Python
-        uses: ./.github/actions/setup-python
+      # Python 3.13 breaks wptrunner, so pin the version until
+      # web-platform-tests/wpt#48585 is fixed.
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
       - name: Prep test environment
         run: |
           gtar -xzf target.tar.gz
+          python3 -m pip install --upgrade pip
           python3 ./mach bootstrap --skip-lints
       - name: Smoketest
         run: python3 ./mach smoketest --${{ inputs.profile }}