Update page.mdx (#8366)

changed custom start command

www/apps/resources/app/deployment/medusa-application/railway/page.mdx

@@ -264,7 +264,7 @@ To set the `start` command of your Medusa application in server mode:
 4. For the “Custom Start Command” field, enter the following and click the check mark button:
 
 ```bash npm2yarn
-npm run redeploy && npm run start
+npm run predeploy && npm run start
 ```
 
 ### Deploy Changes