Update Synchronization source change paragraph

to explicitly refer to the synchronizationSourceId property as per BCP-008-01

docs/Overview.md

@@ -194,7 +194,7 @@ previousSync:0x70:35:09:ff:fe:c7:da:00 from NIC1, currentSync: 0x00:0c:ec:ff:fe:
 
 #### Synchronization source change
 
-When devices are configured to use external synchronization they MUST publish the synchronization source id currently being used and update the `externalSynchronizationStatus` property whenever it changes, using `null` if a synchronization source cannot be discovered. Devices which are not using external synchronization MUST populate this property with `internal` or their own id if they themselves are the synchronization source (e.g. the device is a grandmaster).
+When devices are configured to use external synchronization they MUST publish the synchronization source id currently being used in the `synchronizationSourceId` property and update the `externalSynchronizationStatus` property whenever it changes, using `null` if a synchronization source cannot be discovered. Devices which are not using external synchronization MUST populate this property with `internal` or their own id if they themselves are the synchronization source (e.g. the device is a grandmaster).
 
 When devices suffer a synchronization source change the `externalSynchronizationStatus` property MUST temporarily transition to a `PartiallyUnhealthy` state. It can then return to a different state if the operating conditions match it more closely (returning to a healthier state MUST respect the requirements in the [status reporting delay section](#sender-status-reporting-delay)).