Do only replace the first occurrence of redirects.

The first occurrence of the redirect tag is the mw redirect token
and will be changed by the bot.
All the others may be prosa and kept unchanged.

This PS do not change redirects inside comments anymore;
see https://en.wikipedia.org/wiki/Special:PermanentLink/619532917#Bot_messed_up_HTML_comments_while_fixing_double_redirect

Change-Id: I456b1e6635570e2cf0e5892558b19dede060b35e
Merge "Do only replace the first occurrence of redirects."