[2p2cni] update reference solutions

A lot has been changed in the test setting from the 2.12 release:
boundary condition types, evaluation points for boundary condition
values and spatial parameters, domain heterogeneity, complexity of
the fluid system relations, Newton and linear solver tolerances,
maximum time step size. Synchronizing the settings between 2.12 and
master renders the differences negligibly small. Keep the new
setting, uncomment the domain heterogeneity, simplify the Neumann
boundary condition, adapt the reference solution.