applets/systemtray: suppress main text of tooltip matching visible text
Reason for the change
In this case it simply repeats what you can already see; there's no reason to show it in the tooltip. This makes the tooltip text more relevant.
Test plan
Hover over a System Tray item in the hidden/expanded view that would normally have a tooltip title that's identical to the visible text, but also normally shows subtitle text. For example, Notifications.
There's no effect for items in the visible layout on the panel.
Screenshots or screen recordings
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