Update selector for chat view menu

[mquevill]

Using "role=navigation" is no longer unique enough to get the view menu. This led to 7 match results (at least in my case) for '[role=navigation] > div > div', which defaults to the selectMenuItem() use case.

[The users' interfaces seem to be more unified now, so we could consider eliminating the "new sidebar" checks too, since those may be artifacts from multiple versions ago.]

Fixes #2178.