For images smaller than the viewport at 100% zoom, Gwenview allows to
scale up the image to {nav Fit} the window if {nav Enlarge smaller images}
is checked in the configuration dialog. So far this only worked for
raster-based images, but not for SVGs.
`mEnlargeSmallerImages` is meant to be handled by the abstract base
class `AbstractImageView`, however when f00cef3c0 moved code over there
from `RasterImageView`, it was missed to also adapt `SvgImageView`. This
can be fixed by implementing the missing function.
In addition, a left-over `bool` is removed.
BUG: 364822