Fix a typo in Transaction
We parse v1, v2, and v3 transactions, but we don't validate them,
due to the Sapling checkpoint.
@@ -40,7 +40,7 @@ use crate::{
///
/// Zcash has a number of different transaction formats. They are represented
/// internally by different enum variants. Because we checkpoint on Sapling
-/// activation, we do not parse any pre-Sapling transaction types.
+/// activation, we do not validate any pre-Sapling transaction types.
#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
// XXX consider boxing the Optional fields of V4 txs
#[allow(clippy::large_enum_variant)]
