[py] fix grammar error

Author: cgoldberg

py/conftest.py

@@ -114,7 +114,7 @@ def driver(request):
     if (driver_class == "Ie") and _platform != "Windows":
         pytest.skip("IE and EdgeHTML Tests can only run on Windows")
     if "WebKit" in driver_class and _platform == "Windows":
-        pytest.skip("WebKit tests can not be run on Windows")
+        pytest.skip("WebKit tests cannot be run on Windows")
 
     # conditionally mark tests as expected to fail based on driver
     marker = request.node.get_closest_marker(f"xfail_{driver_class.lower()}")