Update release notes 1.13.1 (#1063)

Author: cliu123

release-notes/opendistro-for-elasticsearch-security.release-notes-1.13.1.0.md

@@ -5,7 +5,9 @@ Compatible with Elasticsearch 7.10.2
 ### Bug fixes
 
 * Fix for "java.lang.IllegalArgumentException: The array of keys must not be null" for "_cat/health" requests ([#1048](https://github.com/opendistro-for-elasticsearch/security/pull/1048))
+* Revert "Fix AuthCredentials equality (#876)" to improve performance ([#1061](https://github.com/opendistro-for-elasticsearch/security/pull/1061))
 
 ### Maintenance
 
 * Bump version to 1.13.1.0 ([#1054](https://github.com/opendistro-for-elasticsearch/security/pull/1054))
+* Update release notes 1.13.1 ([#1063](https://github.com/opendistro-for-elasticsearch/security/pull/1063))