refactor: update delorean_segment_store/src/column.rs

Co-authored-by: Andrew Lamb <alamb@influxdata.com>

delorean_segment_store/src/column.rs

@@ -61,6 +61,7 @@ impl Column {
         0
     }
 
+    /// Returns the (min, max)  values stored in this column
     pub fn column_range(&self) -> Option<(Value<'_>, Value<'_>)> {
         match &self {
             Column::String(meta, _) => match &meta.range {