docs(medusa-file-s3): update aws config object name (#5098)

Update the aws config object name as [defined here](https://github.com/medusajs/medusa/blob/develop/packages/medusa-file-s3/src/services/s3.ts#L43)

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

packages/medusa-file-s3/README.md

@@ -50,7 +50,7 @@ const plugins = [
       region: process.env.S3_REGION,
       access_key_id: process.env.S3_ACCESS_KEY_ID,
       secret_access_key: process.env.S3_SECRET_ACCESS_KEY,
-      aws_config_option: {},
+      aws_config_object: {},
     },
   },
 ]