Really fix hit testing in the generic wxDataViewToggleRenderer.

The changes of r73835 fixed hit testing in horizontal direction but broke it
in the vertical one as the computed checkbox rectangle was not relative to the
cell rectangle as it should have been. Do fix this now.

See #15144.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73838 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775