Update index.md

fix typo in document

Signed-off-by: mqliang mqliang.zju@gmail.com
Signed-off-by: lmq <mqliang@lmqs-MacBook-Pro.local>

docs/userguide/storagedriver/index.md

@@ -13,7 +13,7 @@ weight = 7
 
 # Docker storage drivers
 
-Docker relies on driver technology to manage the storage and interactions associated with images and they containers that run them. This section contains the following pages:
+Docker relies on driver technology to manage the storage and interactions associated with images and the containers that run them. This section contains the following pages:
 
 * [Understand images, containers, and storage drivers](imagesandcontainers.md)
 * [Select a storage driver](selectadriver.md)