get rid of bad copy and paste

Author: silesky

src/connections/sources/catalog/libraries/server/node/migration.md

@@ -60,8 +60,6 @@ If you're using the [classic version of Analytics Node.js](/docs/connections/sou
     ```
 * The `flushAt` configuration option changed to `maxEventsInBatch`.
 
-* The `flushAt` configuration option changed to `maxEventsInBatch`.
-
 * The `enable` setting (for disabling analytics during tests) became `disable`. `enable: false` changed to `disable: true`.
 
 #### Removals