Fix PINA/tutorials/tutorial2 0.2 version

[ndem0]

Traceback (most recent call last):
  File "/home/matte_b/PINA/tutorials/tutorial2/tutorial.py", line 56, in <module>
    class Poisson(SpatialProblem):
  File "/home/matte_b/PINA/tutorials/tutorial2/tutorial.py", line 68, in Poisson
    'gamma1': Condition(location=CartesianDomain({'x': [0, 1], 'y':  1}), equation=FixedValue(0.)),
File "/home/matte_b/PINA/pina/condition/condition.py", line 65, in __new__
    raise ValueError(f"Invalid keyword arguments {kwargs.keys()}.")
ValueError: Invalid keyword arguments dict_keys(['location', 'equation']).