Fix duplicate Jon Harald Søby in CREDITS

Fix duplicate Jon Harald Søby in CREDITS

There are some commits from “jhsoby <jhsoby@gmail.com>”. Update the
.mailmap to correct the name of those commits (the existing line would
only update <jhsoby@users.mediawiki.org> commits), and remove the jhsoby
line from the CREDITS.

Also remove jeblad from CREDITS – he already has a .mailmap entry
mapping <john.blad@wikimedia.de> to John Erling Blad, but
maintenance/updateCredits.php never removes CREDITS entries, so while it
adds a correct John Erling Blad entry it won’t remove jeblad by itself.

Change-Id: I987d1cb1e5190899d944c0880211296580abbcb6