fix typo

Author: omahs

docs/prepare-db-upgrade.md

@@ -37,7 +37,7 @@ The `compatibility` field takes one of four values:
 
  * **breaking**: the step is unsafe and will prevent certain queries from working.
 
-The `some_relation.rel` line(s) are the actions required to perform the database upgrade. Do a diff on the the new vs old `.dbscheme` file to get an idea of what they have to achieve. Sometimes you won't need any upgrade commands – this happens when the dbscheme has changed in "cosmetic" ways, for example by adding/removing comments or changing union type relationships, but still retains the same on-disk format for all tables; the purpose of the upgrade script is then to document the fact that it's safe to replace the old dbscheme with the new one.
+The `some_relation.rel` line(s) are the actions required to perform the database upgrade. Do a diff on the new vs old `.dbscheme` file to get an idea of what they have to achieve. Sometimes you won't need any upgrade commands – this happens when the dbscheme has changed in "cosmetic" ways, for example by adding/removing comments or changing union type relationships, but still retains the same on-disk format for all tables; the purpose of the upgrade script is then to document the fact that it's safe to replace the old dbscheme with the new one.
 
 Ideally, your downgrade script will perfectly revert the changes applied by the upgrade script, such that applying the upgrade and then the downgrade will result in the same database you started with.