[Communication]: Update ChangeLog files for March Release (#633)

* Updaet ChangeLog files for March Release

* Update sdk/communication/azure-communication-common/CHANGELOG.md

Co-authored-by: JoshuaLai <[email protected]>

* Update sdk/communication/azure-communication-chat/CHANGELOG.md

Co-authored-by: JoshuaLai <[email protected]>

Co-authored-by: JP Chen <[email protected]>
Co-authored-by: JoshuaLai <[email protected]>

Author: 3 people

sdk/communication/azure-communication-chat/CHANGELOG.md

@@ -1,6 +1,6 @@
 # Release History
 
-## 1.0.0-beta.7 (Unreleased)
+## 1.0.0-beta.7 (2021-03-09)
 ### Added
 - Support real time notifications with new methods in ChatClient/ChatAsyncClient: 
     - startRealtimeNotifications

sdk/communication/azure-communication-common/CHANGELOG.md

@@ -1,6 +1,6 @@
 # Release History
 
-## 1.0.0-beta.7 (Unreleased)
+## 1.0.0-beta.7 (2021-03-09)
 ### Breaking Changes
 - Credential `getToken` returns the newly added `CommunicationAccessToken` object instead of `AccessToken`.
 - Renamed 'getRefreshProactively' to 'isRefreshProactively' in 'CommunicationTokenRefreshOptions'