Changelog entry for dissolve delay issue (dfinity#5580)

# Motivation

Changelog entry was missing from
dfinity#5560

# Changes

Added missing changelog entry.

# Tests

no

# Todos

- [x] Add entry to changelog (if necessary).

CHANGELOG-Nns-Dapp-unreleased.md

@@ -23,6 +23,7 @@ proposal is successful, the changes it released will be moved from this file to
 #### Fixed
 
 * Bug where neurons are displayed as eligible to vote, even though they have already voted.
+* Issue with setting exact dissolve delay on SNS neurons.
 
 #### Security