[bugfix] Fix the outputlang parameter in listpages.py
[bugfix] Fix the outputlang parameter in listpages.py

The listpages parameter -format:7 needs -outputlang to be set. But it can not
be set because of this typo.

Change-Id: I4b8147585d5598382b740acc485900af63c2838c

PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core