Final piece of search-and-replace

doc/update/8.11-to-8.12.md

@@ -185,7 +185,7 @@ If all items are green, then congratulations, the upgrade is complete!
 ### 1. Revert the code to the previous version
-Follow the [upgrade guide from 8.9 to 8.11](8.9-to-8.11.md), except for the
+Follow the [upgrade guide from 8.10 to 8.11](8.10-to-8.11.md), except for the
 database migration (the backup is already migrated to the previous version).
 ### 2. Restore from the backup