Utilities: replaced "@c Units" with "@ref Units".
Utilities: replaced "@c Units" with "@ref Units".

nickerso/libcellml,cellml/libcellml,cellml/libcellml,hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml,cellml/libcellml,cellml/libcellml,nickerso/libcellml,hsorby/libcellml,hsorby/libcellml