[VnV][telemac3d] Update stratif_wind example with better choices for keywords

- TIDAL FLATS = YES (default value) to improve mass conservation (water depth
+ tracer, water depth up to machine accuracy)
- SOLVER FOR PROPAGATION = 7 (GMRES = default) as the most efficient
- with theses choices of solvers, accuracies for propagation and PPE can be set
to default = 1.E-8
- ==> less differences between sequential and parallel runs