[FIX] upload: Increase stack depth of warnings
[FIX] upload: Increase stack depth of warnings

The `APISite.upload` method is decorated which causes an additional layer in
the stack. This is increasing the depth of each warning accordingly.

Change-Id: I0a2e04a7178600deaa040e002004eee886ca2c1c

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