Removed unused <variant> inclusion.
Removed unused <variant> inclusion.

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