diffusivity name change (#12633)
diffusivity name change
(#12633)

jessecarterMOOSE/moose,SudiptaBiswas/moose,lindsayad/moose,lindsayad/moose,laagesen/moose,idaholab/moose,harterj/moose,lindsayad/moose,milljm/moose,jessecarterMOOSE/moose,jessecarterMOOSE/moose,idaholab/moose,SudiptaBiswas/moose,dschwen/moose,harterj/moose,sapitts/moose,idaholab/moose,idaholab/moose,andrsd/moose,YaqiWang/moose,nuclear-wizard/moose,SudiptaBiswas/moose,dschwen/moose,nuclear-wizard/moose,sapitts/moose,harterj/moose,milljm/moose,permcody/moose,SudiptaBiswas/moose,YaqiWang/moose,sapitts/moose,laagesen/moose,lindsayad/moose,dschwen/moose,idaholab/moose,bwspenc/moose,bwspenc/moose,andrsd/moose,YaqiWang/moose,harterj/moose,andrsd/moose,laagesen/moose,dschwen/moose,bwspenc/moose,permcody/moose,milljm/moose,nuclear-wizard/moose,lindsayad/moose,YaqiWang/moose,permcody/moose,laagesen/moose,laagesen/moose,harterj/moose,permcody/moose,bwspenc/moose,andrsd/moose,andrsd/moose,sapitts/moose,milljm/moose,jessecarterMOOSE/moose,jessecarterMOOSE/moose,sapitts/moose,SudiptaBiswas/moose,dschwen/moose,nuclear-wizard/moose,bwspenc/moose,milljm/moose