doc fix

Signed-off-by: Adam Gutglick <adam@spiraldb.com>

Author: AdamGS

encodings/parquet-variant/src/array.rs

@@ -45,9 +45,7 @@ use vortex_mask::Mask;
 ///
 /// 2. **Value child nullability**: the `value` child is `Binary` and may be nullable or
 ///    non-nullable. In partially-shredded layouts some rows have their data in `typed_value`
-///    instead, so the corresponding `value` slot is null — making the child nullable. This
-///    nullability is persisted in [`ParquetVariantMetadata::value_nullable`] so that
-///    serialization round-trips preserve the original Arrow field nullability.
+///    instead, so the corresponding `value` slot is null — making the child nullable.
 ///
 /// 3. **Typed-value child nullability**: the `typed_value` child carries its own `DType`
 ///    (which includes nullability).
@@ -98,10 +96,8 @@ impl ParquetVariantArray {
                 "typed_value length must match metadata length"
             );
         }
-        let nullability = match &validity {
-            Validity::NonNullable | Validity::AllValid => Nullability::NonNullable,
-            _ => Nullability::Nullable,
-        };
+        let nullability = validity.nullability();
+
         Ok(Self {
             dtype: DType::Variant(nullability),
             validity,