The unified-mailbox rework added settings.appearance.unified_mailbox.
cross_account.{label,description} and sidebar.unified_mailbox, and dropped
the legacy settings.appearance.all_mail.{label,description}, in en and every
other locale except Hebrew (he) and Slovak (sk). Bring he/sk in line so the
translations-completeness test passes (no missing/extra keys vs en).
Stefan Hildebrandt
a8598db44d