Updated mediawiki/extensions
Project: mediawiki/extensions/InviteSignup  ee7d50d848de700f0e0df7cd4ef12b6e7f4c74d9

Clarify signup date table header

Some translated it as a call to action. "Signed up [on]"
is clearer; qqq was updated on wiki.

Change-Id: I177f2275e9ccffff5ae2613083584d93eeb8fff2