[IMPROV] i18n: Deprecate list as code in twtranslate
[IMPROV] i18n: Deprecate list as code in twtranslate

`twtranslate` supports a list as code in order to change it and return the
actually used code. This was only used for `twntranslate` and shouldn't be used
anymore.

Change-Id: I13d45e39ea52d77983fb4e654f8c0772f0263306

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