Rework the slot has_molar_equivalent & has_percentage_of_total #59
Description
https://nfdi-de.github.io/chem-dcat-ap/elements/has_molar_equivalent/ & https://nfdi-de.github.io/chem-dcat-ap/latest/elements/slots/has_percentage_of_total/ are currently wrongly added as slot on ChemicalSubstance, which is defined in the chemical_entities.yaml but these slots are defined in the chemical_reaction.yaml, since they only make sense in the context of a chemical reaction. So it seems best to just drop the two from the slot list of ChemicalSubstance.