Removed docstring on MGXS.xs_tally to eliminate sphinx cross-reference issues
Removed docstring on MGXS.xs_tally to eliminate sphinx cross-reference issues

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