Python3: Remove xfail for wpt unit tests in PY3 (#26202)

Tests in test_wpt.py were marked as xfail due to virtualenv
activation issue (pypa/virtualenv#1710)
This issue has now been solved.

tools/wpt/tests/test_wpt.py

@@ -1,6 +1,5 @@
 import errno
 import os
-import platform
 import shutil
 import socket
 import subprocess
@@ -44,9 +43,6 @@ def get_persistent_manifest_path():
 
 @pytest.fixture(scope="module", autouse=True)
 def init_manifest():
-    # See https://github.com/pypa/virtualenv/issues/1710
-    if sys.version_info[0] >= 3 and platform.system() == "Windows":
-        pytest.xfail(reason="virtualenv activation fails in Windows for python3")
     with pytest.raises(SystemExit) as excinfo:
         wpt.main(argv=["manifest", "--no-download",
                        "--path", get_persistent_manifest_path()])