notification_bundle_base and notification_bundle_display_hash are no longer used now that T120153: Change bundling system to allow individual treatment is done.
SQL:
- https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Echo/+/306846/10/db_patches/patch-drop-notification_bundle_base.sql
- https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Echo/+/306849/9/db_patches/patch-drop-notification_bundle_display_hash.sql
Where: all x1 databases that have an echo_event table (same set as echo.dblist)
Backwards compatible: yes, now that the patches are merged and deployed the software doesn't reference these fields anymore