STYLE: Remove `StackTransform` template argument defaults for dimensions
STYLE: Remove `StackTransform` template argument defaults for dimensions

These defaults appear counter-intuitive. For example, it does not seem logical to have `NOutputDimensions = 3` by default, for `StackTransform<double, 2>`.

SuperElastix/elastix,SuperElastix/elastix,SuperElastix/elastix,SuperElastix/elastix,SuperElastix/elastix