Fix typo in openmc.h
Fix typo in openmc.h

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