[bugfix] Fix bug introduced by backport 377c3fca
The backport has not been adjusted to the old FVAssembler interface. The method gridGeometry was called although in 3.0 the method is called fvGridGeometry.
The backport has not been adjusted to the old FVAssembler interface. The method gridGeometry was called although in 3.0 the method is called fvGridGeometry.