Update dev_setup.rst
Update dev_setup.rst

Making the link to Windows installer for libxml2 more obvious.
hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,hsorby/libcellml,nickerso/libcellml,cellml/libcellml,cellml/libcellml,nickerso/libcellml,cellml/libcellml,nickerso/libcellml,cellml/libcellml,hsorby/libcellml