block_journal: fix typo caught by @akalin-keybase
block_journal: fix typo caught by @akalin-keybase

Issue: #448

keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client