Don't move keyboard focus on button press

Until the spec is clear about how the keyboard focus should be
transferred between sub-surfaces, it's better to remove this heuristic
and focus only the main surface.

For example, if an application window has sub-surfaces but user doesn't
press any pointer button, any sub-surface can have focus.

Effectively, this reverts 55f3a295.
1 job for !253 with work/no-keyboard-focus-on-press in 7 minutes and 41 seconds (queued for 132 minutes and 2 seconds)
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passed linux kf5-qt5 qt5.15 #113366

00:07:41

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