[MPL/RelPermBrooksCorey] Modified some parts in the documentation

Documentation/ProjectFile/properties/property/RelPermBrooksCorey/c_RelPermBrooksCorey.md

-The relative permeability function proposed by Brooks&Corey (1964) \cite BrooksCorey1964.
+\copydoc MaterialPropertyLib::RelPermBrooksCorey

Documentation/ProjectFile/properties/property/RelPermBrooksCorey/t_min_relative_permeability_gas.md

-The minimal relative permeability of the gas (or non-wetting) phase.