message: Fixup a few changelog entries
diff: - The order that sort and distinct are applied can change the query result.
  - Applying an empty sort or distinct descriptor is now a no-op, this
  could previously be used to clear a sort or distinct operation.
  + PR [#2644](https://github.com/realm/realm-core/pull/2644)
  * Support for size query on LinkedList removed. This is perhaps not so
  breaking after all since it is probably not used.
  PR [#2532](https://github.com/realm/realm-core/pull/2532).
  - `size_t Table::find_first(size_t col_ndx, null)`
  - `OutputStream& operator<<(OutputStream& os, const null&)`
  * Add method to get total count of backlinks for a row
  + PR [#2672](https://github.com/realm/realm-core/pull/2672)
  -----------
  