[swimming-dem-pfem] The time settings are not written correctly

[maceligueta]

The format for ProjectParameters.json changed completely and should follow the example:

https://github.com/KratosMultiphysics/Kratos/blob/master/applications/SwimmingDEMApplication/tests/PFEM-DEM_tests/ProjectParameters.json

Apparently is was fixed for Fluid-DEM, because that application is not complaining. We could copy the ideas for the implementation from there.