Use simpler scheme for removing non-WMP XS
Use simpler scheme for removing non-WMP XS

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