removed ifdef guard for openmp when populating fission bank
removed ifdef guard for openmp when populating fission bank

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