Fix moosedocs check command exit code
Fix moosedocs check command exit code

(refs #15996)

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