chore: Adds note about numerical x-axis (#26208)

Co-authored-by: John Bodley <[email protected]>

UPDATING.md

@@ -30,6 +30,10 @@ assists people when migrating to a new version.
 
 ### Other
 
+## 3.0.3
+
+- [26034](https://github.com/apache/superset/issues/26034): Fixes a problem where numeric x-axes were being treated as categorical values. As a consequence of that, the way labels are displayed might change given that ECharts has a different treatment for numerical and categorical values. To revert to the old behavior, users need to manually convert numerical columns to text so that they are treated as categories. Check https://github.com/apache/superset/issues/26159 for more details.
+
 ## 3.0.0
 
 - [25053](https://github.com/apache/superset/pull/25053): Extends the `ab_user.email` column from 64 to 320 characters which has an associated unique key constraint. This will be problematic for MySQL metadata databases which use the InnoDB storage engine with the `innodb_large_prefix` parameter disabled as the key prefix limit is 767 bytes. Enabling said parameter and ensuring that the table uses either the `DYNAMIC` or `COMPRESSED` row format should remedy the problem. See [here](https://dev.mysql.com/doc/refman/5.7/en/innodb-limits.html) for more details.