pywikibot.DataSite.mergeItems must set the bot flag
pywikibot.DataSite.mergeItems must set the bot flag

As for other similar actions, the bot flag must be set by default.

Bug: T138287
Change-Id: Ie57064e77baca596b54cda8308cdd66fb4c67329

happy5214/pywikibot-core,jayvdb/pywikibot-core,PersianWikipedia/pywikibot-core,hasteur/g13bot_tools_new,magul/pywikibot-core,wikimedia/pywikibot-core,jayvdb/pywikibot-core,Darkdadaah/pywikibot-core,hasteur/g13bot_tools_new,happy5214/pywikibot-core,hasteur/g13bot_tools_new,npdoty/pywikibot,npdoty/pywikibot,Darkdadaah/pywikibot-core,wikimedia/pywikibot-core,magul/pywikibot-core