[nit] Panel is referred to as "top bar" / "top panel" in a handful of places

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I suspect this terminology has carried over from the previous GNOME environment in a sense. For example, in Date & Time settings, we have the "Show Date on Top Panel" option. This text makes less sense if the user's panel isn't at the top of the screen:

The Panel entry in the Desktop settings also describes it as a "top bar".