fixed typo in comment
fixed typo in comment

kellyrowland/openmc,mit-crpg/openmc,mit-crpg/openmc,shikhar413/openmc,johnnyliu27/openmc,paulromano/openmc,paulromano/openmc,walshjon/openmc,wbinventor/openmc,liangjg/openmc,johnnyliu27/openmc,amandalund/openmc,wbinventor/openmc,lilulu/openmc,liangjg/openmc,smharper/openmc,walshjon/openmc,kellyrowland/openmc,lilulu/openmc,paulromano/openmc,smharper/openmc,sxds/opemmc,mjlong/openmc,wbinventor/openmc,samuelshaner/openmc,amandalund/openmc,smharper/openmc,bhermanmit/openmc,lilulu/openmc,walshjon/openmc,johnnyliu27/openmc,mjlong/openmc,shikhar413/openmc,samuelshaner/openmc,sxds/opemmc,mit-crpg/openmc,amandalund/openmc,amandalund/openmc,liangjg/openmc,liangjg/openmc,paulromano/openmc,samuelshaner/openmc,johnnyliu27/openmc,smharper/openmc,bhermanmit/openmc,samuelshaner/openmc,shikhar413/openmc,shikhar413/openmc,wbinventor/openmc,mit-crpg/openmc,walshjon/openmc