Apply clang format changes to model.cpp.
Apply clang format changes to model.cpp.

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