Rails4: replace deprecated Relation#first with finder options at UserTest

git-svn-id: http://svn.redmine.org/redmine/trunk@12564 e93f8b46-1217-0410-a6f0-8f06a7374b81
Rails4: replace deprecated Relation#first with finder options at WikiContentTest

git-svn-id: http://svn.redmine.org/redmine/trunk@12565 e93f8b46-1217-0410-a6f0-8f06a7374b81