Only adjust the CookedEditor default staged dir if it's not already been overriden.
[FYI] Josh.Adams
#rb: Josh.Adams
#preflight
#ROBOMERGE-AUTHOR: eric.knapik
#ROBOMERGE-SOURCE: CL 21186791 via CL 21195237 via CL 21195428 via CL 21195504
#ROBOMERGE-BOT: UE5 (Release-Engine-Staging -> Main) (v972-20964824)
[CL 21196929 by eric knapik in ue5-main branch]