changed block diagram to be of .png format

Signed-off-by: Srinadh Penugonda <Srinadh_Penugondaa@dell.com>

Author: spenugondaa

doc/event-alarm-framework/event-alarm-framework-blockdiag.JPG

@@ -183,7 +183,7 @@ EVENT table should support 40k/30-day records. Current active alarms are limited
 
 ## 1.2 Design Overview
 
-![Block Diagram](event-alarm-framework-blockdiag.JPG)
+![Block Diagram](event-alarm-framework-blockdiag.png)
 
 ### 1.2.1 Basic Approach
 The feature involves new development.