Fix S(a,b) temperature indexing in plot_xs
Fix S(a,b) temperature indexing in plot_xs

paulromano/openmc,wbinventor/openmc,walshjon/openmc,amandalund/openmc,liangjg/openmc,johnnyliu27/openmc,smharper/openmc,smharper/openmc,shikhar413/openmc,wbinventor/openmc,liangjg/openmc,walshjon/openmc,smharper/openmc,mit-crpg/openmc,johnnyliu27/openmc,mit-crpg/openmc,bhermanmit/openmc,smharper/openmc,wbinventor/openmc,johnnyliu27/openmc,shikhar413/openmc,amandalund/openmc,mit-crpg/openmc,paulromano/openmc,johnnyliu27/openmc,amandalund/openmc,walshjon/openmc,shikhar413/openmc,paulromano/openmc,paulromano/openmc,liangjg/openmc,bhermanmit/openmc,amandalund/openmc,mit-crpg/openmc,liangjg/openmc,wbinventor/openmc,shikhar413/openmc,walshjon/openmc