message: Add query_one to postgres::Transaction
  I believe this was missed in
diff: @@ -58,6 +58,14 @@ impl<'a> Transaction<'a> {
  executor::block_on(self.0.query(query, params))
  }
  + /// Like `Client::query_one`.
  + pub fn query_one<T>(&mut self, query: &T, params: &[&(dyn ToSql + Sync)]) -> Result<Row, Error>
  + where
  + T: ?Sized + ToStatement,
  + {
  + executor::block_on(self.0.query_one(query, params))
  + }
  +
  /// Like `Client::query_raw`.
  pub fn query_raw<'b, T, I>(
  &mut self,
  