Fix INTERVAL sort order doc to be undefined (#222)
diff --git a/src/main/thrift/parquet.thrift b/src/main/thrift/parquet.thrift
index 9decb5a..2084ac6 100644
--- a/src/main/thrift/parquet.thrift
+++ b/src/main/thrift/parquet.thrift
@@ -945,7 +945,7 @@
* TIME_MICROS - signed comparison
* TIMESTAMP_MILLIS - signed comparison
* TIMESTAMP_MICROS - signed comparison
- * INTERVAL - unsigned comparison
+ * INTERVAL - undefined
* JSON - unsigned byte-wise comparison
* BSON - unsigned byte-wise comparison
* ENUM - unsigned byte-wise comparison