add release note

Author: fneum

doc/release_notes.rst

@@ -11,6 +11,8 @@ Release Notes
 Upcoming Release
 ================
 
+* The default configuration for the emission reduction path in myopic pathway planning mode has been changed to align more closely with policy targets (``co2_budget:``).
+
 * Bugfix: Adjusted existing heating data in ``build_existing_heating_distribution`` and the indexing of existing heat pumps for the COP correction in ``add_brownfield`` to make the myopic code work with the geothermal district heating feature.
 
 * Restore share policy "base" functionality to share build renewable profiles