Solve a deprecated warning in the integrator function for CasADi 3.6.3

[brunomorampc]

The following deprecation warning occour with the version 3.6.3 of CasADi.

The same functionality is provided by providing additional input arguments to the 'integrator' function, in particular:
 * Call integrator(..., t0, tf, options) for a single output time, or
 * Call integrator(..., t0, grid, options) for multiple grid points.
The legacy 'output_t0' option can be emulated by including or excluding 't0' in 'grid'.
Backwards compatibility is provided in this release only.") [.../casadi/core/integrator.cpp:515]```

In [this line](https://github.com/hilo-mpc/hilo-mpc/blob/master/hilo_mpc/modules/base.py#L1713). 
It seems that the t0 and tf and grid needs to be passed as argument and not anymore in the options. 

We need to decide if we want to abandon the other version of casadi and update to the new one or allow compatibility with older versions