Remove superfluous re- from confirmemail_body_set

We can't know if the email had ever been set before.
And it doesn't matter.
<https://translatewiki.net/wiki/Thread:Translating_talk:MediaWiki/About_MediaWiki:Confirmemail_body_set/en>

Change-Id: I88ae448ac6a4742ae42dd354ff784c2506105313