Fix deprecation in specs
Created by: zzet
DEPRECATION: expect { }.not_to raise_error(SpecificErrorClass)
is deprecated. Use expect { }.not_to raise_error
(with no args) instead. Called from /home/travis/build/gitlabhq/gitlabhq/spec/tasks/gitlab/backup_rake_spec.rb:42:in `block (4 levels) in <top (required)>'.