Remove URP Terrain Sample to save package space

[diogovtx]

There's already a terrain sample on ASP, which is the big package.

[Dawie3565]

There are 4 functions in ASP for terrain samples + one sub function.

BIRP / URP --- Terrain 4 Layer --- Terrain 4 Layer BasePass

HDRP --- Terrain 8 Layer --- Terrain 8 Layer BasePass

ASP has two terrain demos in all pipelines BIRP, HDRP and URP Terrain Simple Terrain Snow

Note ASP functions for terrain also have one sub function called "Saturation" that is also only found in ASP. --- Saturation

this Saturation function uses Grayscale using a dot product with the perceptual weights for the snow option.

[Dawie3565]

closed moved to ASP