Bug 1658296 - Add extra kwargs required by wpt run, r=maja_zf

Differential Revision: https://phabricator.services.mozilla.com/D86567

testing/web-platform/mach_commands.py

@@ -138,6 +138,8 @@ class WebPlatformTestsRunnerSetup(MozbuildObject):
         kwargs["channel"] = None
         kwargs["prompt"] = True
         kwargs["install_browser"] = False
+        kwargs["install_webdriver"] = None
+        kwargs["affected"] = None
 
         # Install the deps
         # We do this explicitly to avoid calling pip with options that aren't