Remove differential aileron mixing for flying wings

This change removes aileron differential and increases the pitch travel slightly.

Differential aileron mixing is not recommended for flying wings as it usually results in pitch input while rolling.

Bench testing looks good. Will change the other mixers (ie: FMU_FX79, FMU_X5, FMU_delta, etc.) after a flight test though. This mixer is currently used by the Wing Wing, Camflyer Q and FX-61.