Update release notes

Author: fredericDelaporte

releasenotes.txt

@@ -3,7 +3,7 @@
 
 Release notes - NHibernate - Version 5.3.0
 
-213 issues were resolved in this release.
+214 issues were resolved in this release.
 
     ##### Possible Breaking Changes #####
         * A distributed cache may hold conflicting timestamps after upgrade for as much as twelve hours.
@@ -123,6 +123,7 @@ Release notes - NHibernate - Version 5.3.0
    * #2156 Support basic arithmetic operations (+, -, *, /) in QueryOver
    * #2135 Support OData GroupBy/Aggregate
    * #2116 Ability to replace ConfigurationManager with a custom config provider
+   * #2108 Multi-Tenancy: Implement tenant per Database strategy
    * #2107 Port Hibernate's Aggregate functions for subqueries
    * #2106 Port Hibernate's support subqueries in HQL as CASE statement alternatives
    * #2100 Allow to override default types with length or precision parameters