Doc: Fix typo slection -> selection
Doc: Fix typo slection -> selection

Task-number: QTBUG-25577
Change-Id: I383584426e0981750db4921490143b0fc46d5d88
Reviewed-by: Casper van Donderen <808524cef5c654648bea2a2b954f3b3445ed083c@nokia.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc