Update release notes

release-notes/5.12.4.md

 # CiviCRM 5.12.4
 
-Released April 20, 2019
+Released April 25, 2019
 
 - **[Synopsis](#synopsis)**
 - **[Bugs resolved](#bugs)**
@@ -21,7 +21,9 @@ Released April 20, 2019
 
 ## <a name="bugs"></a>Bugs resolved
 
-- **Fix mailing preview fails when viewUrl token present and mailing hash enabled." ([dev/core#891](https://lab.civicrm.org/dev/core/issues/891): [14092](https://github.com/civicrm/civicrm-core/pull/14124))**
+- **Fix mailing preview fails when viewUrl token present and mailing hash enabled. ([dev/core#891](https://lab.civicrm.org/dev/core/issues/891): [14124](https://github.com/civicrm/civicrm-core/pull/14124))**
+
+- **Fix drop query testing utf8mb4 support in installation process. ([dev/core#880](https://lab.civicrm.org/dev/core/issues/880): [14129](https://github.com/civicrm/civicrm-core/pull/14129))**
 
 ## <a name="credits"></a>Credits