add commented out validation implementation

Author: ptravers

src/persist-client/src/batch.rs

@@ -1294,6 +1294,19 @@ pub(crate) fn validate_truncate_batch<T: Timestamp>(
         }
     }
 
+    // NB(ptravers): see `compare_and_append_batch`.
+    //let batch = &batch.desc;
+    //if !PartialOrder::less_equal(batch.lower(), truncate.lower())
+    //    || PartialOrder::less_than(batch.upper(), truncate.upper())
+    //{
+    //    return Err(InvalidUsage::InvalidBatchBounds {
+    //        batch_lower: batch.lower().clone(),
+    //        batch_upper: batch.upper().clone(),
+    //        append_lower: truncate.lower().clone(),
+    //        append_upper: truncate.upper().clone(),
+    //    });
+    //}
+
     Ok(())
 }