Match/check the return value of the Supervisor in application.ex to make certain misconfiguration errors more clear
This is a really small change, result should be matched to {:ok, pid} at https://git.pleroma.social/pleroma/pleroma/-/blob/develop/lib/pleroma/application.ex?ref_type=heads#L122
in case of an :error, the result is swallowed up instead of printed, and the user is likely to see a generic Ecto failure instead of why the tree failed to start