doc: Speed up TS migration command (typeorm#7568)

Kudos to @AmauryLiet

Author: Minishlink

docs/migrations.md

@@ -148,7 +148,7 @@ typeorm migration:run
 
 Example with `ts-node`:
 ```
-ts-node ./node_modules/typeorm/cli.js migration:run
+ts-node --transpile-only ./node_modules/typeorm/cli.js migration:run
 ```
 
 This command will execute all pending migrations and run them in a sequence ordered by their timestamps.