Improve 2.16.23 release notes

Mention two important bug fixes in noteDb migration.

Change-Id: Ic913bd8a1add1cb379f8189436975b0fc6afc75c
diff --git a/pages/site/releases/2.16.md b/pages/site/releases/2.16.md
index 87ba5db..d1c2b99 100644
--- a/pages/site/releases/2.16.md
+++ b/pages/site/releases/2.16.md
@@ -648,9 +648,15 @@
 
   * Log the NoteDb migration progress every 1000 changes.
 
+  * Fix contention on single database connection which all migration threads were
+  competing for. Instead use one database connection per thread.
+
+  * Update noteDb status in chunks to avoid an excessive number of DB connections
+  is used.
+
   * Use multiple threads per project for improving the performance when there are
-  a lot of changes per project. The impact is negligible on projects with a limited number
-  of changes.
+  a lot of changes per project. The impact is negligible on projects with a limited
+  number of changes.
 
   * Ensure that all exceptions happening during the migration are properly logged.