[VnV][telemac3d] Update particles example with better choices for a few keywords

- use of gradient conjugate + preconditioning 34 = 2*17 to solve PPE, more
efficient than GMRES for this example
- switch from characteristics to defaul advection scheme for velocities (LIPS)
to decrease differences between sequential and parallel runs
- use preconditioning 34 for the diffusion of velocities (a little bit more
efficient)
- default accuracies for propagation and PPE with this setting of solvers
(1.E-8)