Fix trivial typo in CmdSethandler documentation.
Fix trivial typo in CmdSethandler documentation.

titeuf87/evennia,shollen/evennia,mrkulk/text-world,emergebtc/evennia,feend78/evennia,emergebtc/evennia,feend78/evennia,jamesbeebop/evennia,ergodicbreak/evennia,feend78/evennia,ypwalter/evennia,ypwalter/evennia,mrkulk/text-world,ergodicbreak/evennia,titeuf87/evennia,titeuf87/evennia,TheTypoMaster/evennia,titeuf87/evennia,shollen/evennia,mrkulk/text-world,ypwalter/evennia,feend78/evennia,TheTypoMaster/evennia,jamesbeebop/evennia,mrkulk/text-world,jamesbeebop/evennia,ergodicbreak/evennia,TheTypoMaster/evennia,emergebtc/evennia