message: Update the SyncLeap validation
diff: @@ -173,17 +173,11 @@ impl FetcherItem for SyncLeap {
  // TODO: Possibly check the size of the collections.
  // The header chain should only go back until it hits _one_ switch block.
  - if !self.trusted_block_header.is_switch_block() {
  - for header in iter::once(&self.trusted_block_header)
  - .chain(self.trusted_ancestor_headers.iter())
  - .rev()
  - .skip(1)
  - {
  + for header in self.trusted_ancestor_headers.iter().rev().skip(1) {
  if header.is_switch_block() {
  return Err(SyncLeapValidationError::UnexpectedSwitchBlock);
  }
  }
  - }
  // All headers must have the same protocol versions: sync leaps across upgrade boundaries
  // are not supported.
  