Modify README.md for update server

- modify README.md file

Signed-off-by: kevin <kppw99@gmail.com>
Change-Id: Ic58dbaab6b42d8f6f499c265ec259daecbac1a02

Author: kppw99

update_server/README.md

@@ -5,4 +5,4 @@ The update server is implemented to update tzMon CA and TA.
 Figure 1 explain a detailed protocol.
 
 > <img src="../img/secure_update.jpg" width="400"></img>
-> Figure 1. Secure Update Protocol
+Figure 1. Secure Update Protocol