win32: Don't multiply the scroll event deltas by the Windows scroll lines setting...

win32: Don't multiply the scroll event deltas by the Windows scroll lines setting. See #1408

GTK widgets expect the scroll deltas to be 1 or -1 and calculate a scroll value from that.
Multiplying the delta by the Windows scroll line setting (which defaults to 3) results
in a much larger delta and vastly different behaviour for running a GTK app on Windows
vs on Linux. For example text view and tree view scroll by 9 lines per scroll wheel tick
per default this way while on Linux it is around 3.

Remove the multiplication for now.

See !426 for the gtk3 MR