Parametrize initial condition in llw2d properly

[tkoskela]

In

ParticleDA.jl/test/model/llw2d.jl

Line 210 in cb439b6

function initheight!(height::AbstractMatrix{T},

there are still some hard-coded parameters (e.g. 4, 0.25) that should be parametrised for using Mariya's model.