Bug 1368262 - Disable webdriver test that behaves differently on dev edition vs release, r=ato

The test times out on master and dev edition but not on normal beta. Since
this is difficult to handle in ini files just disable the entire test until there's
a proepr fix for the underlying issue.

MozReview-Commit-ID: B3d7MElHy86

--HG--
extra : rebase_source : eaff065fb42f046173281c713c55ec6a977da812

testing/web-platform/meta/webdriver/navigation.py.ini

@@ -1,5 +1,6 @@
 [navigation.py]
   type: wdspec
+  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1368262
   expected: TIMEOUT
   [navigation.py::test_get_current_url_alert_prompt]
     expected: FAIL