Update changelog as per PR#20426 (Azure#20616)

* Update changelog as per PR#20426

* Update ChangeLog.md

Co-authored-by: Yeming Liu <[email protected]>

Author: imsiddhartha

src/TrafficManager/TrafficManager/ChangeLog.md

@@ -18,6 +18,7 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
+* Added a new optional parameter `AlwaysServe` for endpoints.
 
 ## Version 1.1.0
 * Added two new optional parameters 'MinChildEndpointsIPv4' and 'MinChildEndpointsIPv6' for nested endpoints