Tutorial documentation requires bug fix

[pz-max]

PyPSA-Eur documentation: https://pypsa-eur.readthedocs.io/en/latest/tutorial.html

These parts are not aligned well:

We can also decide which weather data source should be used to calculate potentials and capacity factor time-series for each carrier. For example, we may want to use the ERA-5 dataset for solar and not the default SARAH-2 dataset.

      y: [46., 56.]
    corine: [44, 255]
    natura: true

Finally, it is possible to pick a solver. For instance, this tutorial uses the open-source solvers CBC and Ipopt and does not rely on the commercial solvers Gurobi or CPLEX (for which free academic licenses are available).

    algorithm: kmeans # choose from: [hac, kmeans]
      p_nom_min: sum
      p_min_pu: mean

[pz-max]

Instead of referring to lines we should use start-at or end-at as done here: https://github.com/pypsa/pypsa-eur/blob/master/doc/tutorial.rst