tox: split envlist to one entry per line
tox: split envlist to one entry per line

When a list is rather long, it is easier to read when each element is on
its own line. Diff are also easier to read when the list are altered.

Split elements from tox.ini 'envlist'.

Change-Id: I144717f05ed3c5a7409a9d6c13e0b61767fb42d3

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