Bad `:/` group names coming from test-verify-wpt

[suhaibmujahid]

Until bug 1688043 is fixed, we might want to filter them out similar to ae1682d.

[suhaibmujahid]

Marco found an example coming from test-macosx1470-64/debug-test-verify-wpt-2

push = Push("3a14f1413fdb15bab479659d30a32cbc72f80654")
print(len(push.tasks))
for parent in push._iterate_parents(max_depth=77):
    for task in parent.tasks:
        if not isinstance(task, TestTask):
            continue

        if "testing/web-platform/tests/" in task.groups or "testing/web-platform/tests" in task.groups:
            print(task.id)