message: Avoid exposign schema from segment_reader
diff: @@ -70,10 +70,6 @@ impl SegmentReader {
  self.segment_meta.num_docs()
  }
  - pub fn schema(&self) -> &Schema {
  - &self.schema
  - }
  -
  /// Return the number of documents that have been
  /// deleted in the segment.
  pub fn num_deleted_docs(&self) -> DocId {
  