Mark CheckedHrpstringError instances as no-export

The details of these errors aren't particularly relevant, and its
not worth the effort of exporting them, so we just mark them
no-export here.

Backport of 16aabce

Author: TheBlueMatt

lightning-invoice/src/lib.rs

@@ -91,7 +91,10 @@ use crate::ser::Base32Iterable;
 #[allow(missing_docs)]
 #[derive(PartialEq, Eq, Debug, Clone)]
 pub enum Bolt11ParseError {
-	Bech32Error(CheckedHrpstringError),
+	Bech32Error(
+		/// This is not exported to bindings users as the details don't matter much
+		CheckedHrpstringError,
+	),
 	ParseAmountError(ParseIntError),
 	MalformedSignature(bitcoin::secp256k1::Error),
 	BadPrefix,

lightning/src/offers/parse.rs

@@ -142,7 +142,10 @@ pub enum Bolt12ParseError {
 	/// being parsed.
 	InvalidBech32Hrp,
 	/// The string could not be bech32 decoded.
-	Bech32(CheckedHrpstringError),
+	Bech32(
+		/// This is not exported to bindings users as the details don't matter much
+		CheckedHrpstringError,
+	),
 	/// The bech32 decoded string could not be decoded as the expected message type.
 	Decode(DecodeError),
 	/// The parsed message has invalid semantics.