Reset release notes (#121)

## Summary

Reset `RELEASE_NOTES.md` from `.github/RELEASE_NOTES.template.md` after
the release.

## Validation

- `diff -u .github/RELEASE_NOTES.template.md RELEASE_NOTES.md`
- `git diff --check`

Author: eduardiazf

RELEASE_NOTES.md

@@ -8,20 +8,10 @@
 
 <!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
 
-* Updated `frequenz-api-assets` to `0.3.0`, replacing the old `assets.v1`
-  generated API with `platformassets.v1alpha1`.
-
 ## New Features
 
 <!-- Here goes the main new features and examples or instructions on how to use them -->
 
-* Added client methods for the new `platformassets.v1alpha1` RPCs:
-  `list_gridpools()`, `list_gridpool_energy_schedules()`,
-  `list_market_topology_relations()`, `list_microgrids()`, and
-  `list_microgrid_sensors()`.
-* Added `component_ids` and `categories` filters to
-  `list_microgrid_electrical_components()`.
-
 ## Bug Fixes
 
 <!-- Here goes notable bug fixes that are worth a special mention or explanation -->