Remove comments implying xsi is an undeclared namespace (why did I ever think that?)
Remove comments implying xsi is an undeclared namespace (why did I ever think that?)

jonfoster/pyxb2,jonfoster/pyxb2,balanced/PyXB,jonfoster/pyxb1,jonfoster/pyxb-upstream-mirror,jonfoster/pyxb1,balanced/PyXB,pabigot/pyxb,jonfoster/pyxb-upstream-mirror,CantemoInternal/pyxb,CantemoInternal/pyxb,balanced/PyXB,pabigot/pyxb,CantemoInternal/pyxb,jonfoster/pyxb2,jonfoster/pyxb-upstream-mirror