Corrected an error message in physics.F90:sample_energy, which referred to Law 44 instead of the correct Law 61.
Corrected an error message in physics.F90:sample_energy, which referred to Law 44 instead of the correct Law 61.

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