Add manual page for set low latency funciton

This change adds the manual page for the rmr_set_low_latency()
function.

Issue-ID: RIC-631

Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: I3c5bd0a27ef36c351b2003c34d70f4f09aff8974
diff --git a/docs/rel-notes.rst b/docs/rel-notes.rst
index a8d76f9..f73f2da 100644
--- a/docs/rel-notes.rst
+++ b/docs/rel-notes.rst
@@ -22,6 +22,13 @@
 version 4.0.0, the RMR versions should no longer skip.
 
 
+2020 September 15; Version 4.2.4
+--------------------------------
+
+Add man page for the rmr_set_low_latency() function (RIC-631)
+
+
+
 2020 September 15; Version 4.2.3
 --------------------------------