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

Co-authored-by: John Bodley <4567245+john-bodley@users.noreply.github.com>

UPDATING.md

@@ -24,6 +24,7 @@ assists people when migrating to a new version.
 
 ## Next
 
+- [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.
 - [24657](/~https://github.com/apache/superset/pull/24657): Bumps the cryptography package to augment the OpenSSL security vulnerability.
 
 ### Breaking Changes