[cleanup] Announce Site.has_api method to be removed
[cleanup] Announce Site.has_api method to be removed

Pywikibot core only supports MediaWiki which has API.
Therefore the compat method has_api can be removed after 5 years.

Change-Id: I847894bda56536b70b8609b8d487aee2f4c55b55

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