update changelog entry

Signed-off-by: Rano | Ranadeep <[email protected]>

.changelog/unreleased/breaking-changes/978-identifier-error.md

@@ -1,6 +1,2 @@
-- Remove IdentifierError::Empty and ContainSeparator variants as they
-  are special cases of other existing errors.
-  ([\#978](https://github.com/cosmos/ibc-rs/issues/978))
-- Remove IdentifierError::InvalidLength::length field since it can be
-  deduced from the id.
+- Optimize `IdentifierError` variants and make them mutually exclusive.
   ([\#978](https://github.com/cosmos/ibc-rs/issues/978))