Fix documentation on Annotator get * methods.
Fix documentation on Annotator get * methods.

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