message: subscriber: remove unnecessary transparent attribute
  As far as I can tell, we are not relying on transparency anywhere, so
  using this rather refined feature here is confusing.
diff: @@ -1124,7 +1124,6 @@ impl Default for FmtSpanConfig {
  }
  }
  -#[repr(transparent)]
  pub(super) struct TimingDisplay(pub(super) u64);
  impl Display for TimingDisplay {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  