User does not pass real t and vector state to ode, ode solver does

[ssp3nc3r]

https://github.com/stan-dev/docs/blob/e0afdd2d9419633ce27c89b7616352369235fda8/src/stan-users-guide/odes.Rmd#L141

While real t and vector y (the state variable) must be coded into the first two parameters of the ode function, the user does not pass these to the ode function through the ode solver. Instead, the ode solver endogenously supplies them or builds them up. The vector y will match the initial conditions the user passes to the ode solver: y0, t0, ts.

There may be a better explanation than mine above, but having this in the docs will reduce confusion in knowing what to provide to the ode-function and solver-function pair.

The same explanation should be added to the functions reference in the section:

## Ordinary differential equation (ODE) solvers {#functions-ode-solver}