Modify rename function usage

Signed-off-by: zhouhao <zhouhao@cn.fujitsu.com>

docs/reference/commandline/rename.md

@@ -11,7 +11,7 @@ parent = "smn_cli"
 # rename
 
 ```markdown
-Usage:  docker rename OLD_NAME NEW_NAME
+Usage:  docker rename CONTAINER NEW_NAME
 
 Rename a container
 

man/docker-rename.1.md

@@ -6,7 +6,7 @@ docker-rename - Rename a container
 
 # SYNOPSIS
 **docker rename**
-OLD_NAME NEW_NAME
+CONTAINER NEW_NAME
 
 # OPTIONS
 There are no available options.