Fix link in "Model that learn a probability distribution"

After

- [ ] https://github.com/JuliaAI/MLJBase.jl/pull/1026 is merged

Fix [this link](https://github.com/JuliaAI/MLJModelInterface.jl/blob/86a9845b061fb7bbb8a6b613c5bbb9c71ccadc6f/docs/src/fitting_distributions.md?plain=1#L18) to point to end of `resampling.jl` tests in MLJBase. 