Update 2.12.4 release notes

Change-Id: Iaa184e05a44ffc661811572f15f3cc164f658fe6

ReleaseNotes/ReleaseNotes-2.12.4.txt

diff --git a/ReleaseNotes/ReleaseNotes-2.12.4.txt b/ReleaseNotes/ReleaseNotes-2.12.4.txt
index 3978928..ce2f369 100644
--- a/ReleaseNotes/ReleaseNotes-2.12.4.txt
+++ b/ReleaseNotes/ReleaseNotes-2.12.4.txt
@@ -67,3 +67,4 @@
 * link:https://bugs.chromium.org/p/gerrit/issues/detail?id=4241[Issue 4241]:
 Fix 'Cannot format velocity template' error.
 
+* Fix `sshd.idleTimeout` setting being ignored.