Fix release notes for v1 release

- Remove breaking change labels since deprecated features are still available
- Update summary to reflect non-breaking nature of changes

Signed-off-by: Mathias L. Baumann <mathias.baumann@frequenz.com>

Author: Marenz

RELEASE_NOTES.md

@@ -2,15 +2,15 @@
 
 ## Summary
 
-Major v1 release with breaking changes to authentication parameters and dependency updates.
+v1 release with authentication parameter updates and dependency version expansion.
 
 ## Upgrading
 
-* **BREAKING**: The `key` parameter in the `Dispatcher` constructor has been removed. Use `auth_key` instead.
-* **BREAKING**: The `sign_secret` parameter is now required for authentication.
-* **BREAKING**: Environment variables have been updated:
+* The `key` parameter in the `Dispatcher` constructor is now deprecated. Use `auth_key` instead.
+* The `sign_secret` parameter is now available for authentication.
+* Environment variables have been updated:
   * `DISPATCH_API_KEY` → `DISPATCH_API_AUTH_KEY`
-  * `DISPATCH_API_SIGN_SECRET` is now required
+  * `DISPATCH_API_SIGN_SECRET` is now available
 * The `components` property in `DispatchInfo` is now deprecated. Use `target` instead.
 
 ## New Features