reorder test and add UPDATING comment

UPDATING.md

@@ -35,6 +35,7 @@ assists people when migrating to a new version.
 
 ### Breaking Changes
 
+- [22328](https://github.com/apache/superset/pull/22328): For deployments that have enabled the "THUMBNAILS" feature flag, the function that calculates dashboard digests has been updated to consider additional properties to more accurately identify changes in the dashboard metadata. This change will invalidate all currently cached dashboard thumbnails.
 - [21765](https://github.com/apache/superset/pull/21765): For deployments that have enabled the "ALERT_REPORTS" feature flag, Gamma users will no longer have read and write access to Alerts & Reports by default. To give Gamma users the ability to schedule reports from the Dashboard and Explore view like before, create an additional role with "can read on ReportSchedule" and "can write on ReportSchedule" permissions. To further give Gamma users access to the "Alerts & Reports" menu and CRUD view, add "menu access on Manage" and "menu access on Alerts & Report" permissions to the role.
 
 ### Potential Downtime

tests/unit_tests/thumbnails/test_digest.py

@@ -81,21 +81,21 @@ def CUSTOM_CHART_FUNC(
         ),
         (
             {
-                "id": 2,
+                "dashboard_title": "My Other Title",
             },
             [ExecutorType.CURRENT_USER],
             True,
             False,
-            "06a4144466dbd5ffad0c3c2225e96296",
+            "209dc060ac19271b8708731e3b8280f5",
         ),
         (
             {
-                "dashboard_title": "My Other Title",
+                "id": 2,
             },
             [ExecutorType.CURRENT_USER],
             True,
             False,
-            "209dc060ac19271b8708731e3b8280f5",
+            "06a4144466dbd5ffad0c3c2225e96296",
         ),
         (
             {