add channgelog for the new return code guidance

source/partials/_changelog.erb

@@ -13,6 +13,10 @@
         </thead>
 
     <tbody class="govuk-table__body">
+        <tr class="govuk-table__row">
+            <th class="govuk-table__header">April 3 2024</th>
+            <td class="govuk-table__cell">New guidance "<a href="/integrate-with-integration-environment/prove-users-identity#understand-your-user-s-return-code-claim">Understand your user’s return code claim</a>" which gives information about any issues with the evidence your user provided to prove their identity.</td>
+        </tr>
         <tr class="govuk-table__row">
             <th class="govuk-table__header">Mar 25 2024</th>
             <td class="govuk-table__cell">Remove references to the refresh token and <code>offline_access</code> to simplify integration and the technical flow.</td>