Update release notes

Also the note about some functions becoming non-async, is moved to the
`Upgrading` section, because it is a breaking change.

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

RELEASE_NOTES.md

@@ -6,12 +6,13 @@
 
 ## Upgrading
 
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
+- The `receive_aggregated_data` method now returns a `Receiver`, which provides more flexibility that the previous `AsyncIterator`.
+- The `receive_microgrid_sensors_data`, `receive_single_sensor_data` and `receive_aggregated_data` methods are no-longer `async`.
 
 ## New Features
 
 <!-- Here goes the main new features and examples or instructions on how to use them -->
 
 ## Bug Fixes
 
-* Take out 'async' from  'receive_microgrid_sensors_data' and 'receive_single_sensor_data'.
+<!-- Here goes notable bug fixes that are worth a special mention or explanation -->