Remove unused variable in PolycrystalRandomIC.C
Remove unused variable in PolycrystalRandomIC.C

Refs https://civet.inl.gov/job/967373/ failure on libmesh/libmesh#3171

milljm/moose,harterj/moose,bwspenc/moose,andrsd/moose,sapitts/moose,dschwen/moose,andrsd/moose,bwspenc/moose,lindsayad/moose,idaholab/moose,sapitts/moose,bwspenc/moose,idaholab/moose,sapitts/moose,laagesen/moose,laagesen/moose,lindsayad/moose,laagesen/moose,bwspenc/moose,lindsayad/moose,sapitts/moose,jessecarterMOOSE/moose,milljm/moose,milljm/moose,andrsd/moose,milljm/moose,harterj/moose,jessecarterMOOSE/moose,laagesen/moose,harterj/moose,harterj/moose,laagesen/moose,andrsd/moose,dschwen/moose,lindsayad/moose,idaholab/moose,jessecarterMOOSE/moose,idaholab/moose,dschwen/moose,lindsayad/moose,bwspenc/moose,jessecarterMOOSE/moose,dschwen/moose,idaholab/moose,dschwen/moose,sapitts/moose,milljm/moose,harterj/moose,andrsd/moose,jessecarterMOOSE/moose