Improve definition of `get_neighbors`

[mfeurer]

Currently, it is not documented that get_neighbors operates in the unit hypercube. Also, as it operates in the unit hypercube, the value argument will always be of type float.

[eddiebergman]

No longer relevant in #346 which uses the function name and parameter name as documentation

neighbors_vectorized(vector: f64, ...) and neighbors_values(value: DType, ...)

Deprecation of get_neighbors provides more information as to the deprecation:

    @deprecated("Please use `neighbors_vectorized`  instead.")
    def get_neighbors(
        self,
        value: f64,
        rs: np.random.RandomState,
        number: int | None = None,
        std: float | None = None,
        transform: bool = False,
    ) -> Array[f64]:
        if transform is True:
            raise RuntimeError(
                "Previous `get_neighbors` with `transform=True` had different"
                " behaviour depending on the hyperparameter. Notably numerics"
                " were still considered to be in vectorized form while for ordinals"
                " they were considered to be in value form."
                "\nPlease use either `neighbors_vectorized` or `neighbors_values`"
                " instead, depending on your need. You can use `to_value` or"
                " `to_vector` to switch between the results of the two.",
            )

        if number is None:
            warnings.warn(
                "Please provide a number of neighbors to sample. The"
                " default used to be `4` but will be explicitly required"
                " in the futurefuture.",
                DeprecationWarning,
                stacklevel=2,
            )
            number = 4

        return self.neighbors_vectorized(value, number, std=std, seed=rs)