listpages.py: Fix help docstring
listpages.py: Fix help docstring

Replace -dir with -save in docstring.

Change-Id: Ic17d6255a532c3959ac0924314fe2f01f4d53ea6

PersianWikipedia/pywikibot-core,happy5214/pywikibot-core,smalyshev/pywikibot-core,hasteur/g13bot_tools_new,wikimedia/pywikibot-core,jayvdb/pywikibot-core,h4ck3rm1k3/pywikibot-core,npdoty/pywikibot,jayvdb/pywikibot-core,hasteur/g13bot_tools_new,Darkdadaah/pywikibot-core,h4ck3rm1k3/pywikibot-core,wikimedia/pywikibot-core,npdoty/pywikibot,happy5214/pywikibot-core,magul/pywikibot-core,Darkdadaah/pywikibot-core,darthbhyrava/pywikibot-local,hasteur/g13bot_tools_new,magul/pywikibot-core