chore: add changelog entry

Signed-off-by: joshuaunity <[email protected]>

Author: joshuaunity

documentation/changelog.rst

@@ -21,6 +21,7 @@ New features
 * Separate the ``StorageScheduler``'s tie-breaking preference for a full :abbr:`SoC (state of charge)` from its reported energy costs [see `PR #2023 <https://www.github.com/FlexMeasures/flexmeasures/pull/2023>`_]
 * Improve asset graph hover interaction with a vertical ruler across subcharts, while keeping hover dots for easier visual tracking [see `PR #2079 <https://www.github.com/FlexMeasures/flexmeasures/pull/2079>`_]
 * Improve asset audit log messages for JSON field edits (especially ``sensors_to_show`` and nested flex-config values) [see `PR #2055 <https://www.github.com/FlexMeasures/flexmeasures/pull/2055>`_]
+* Clean up stale sensor references from ``flex-config`` and ``sensors_to_show`` when deleting a sensor, using JSONB queries to find affected assets before pruning those references [see `PR #2106 <https://www.github.com/FlexMeasures/flexmeasures/pull/2106>`_]
 
 Infrastructure / Support
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