Fix helm repo list example

The flags to the command must be provided before the directory: `helm repo index [flags] [DIR]` or an error is given: `Error: This command needs 1 argument: path to a directory`

docs/chart_repository.md

@@ -227,7 +227,7 @@ packaged chart to that directory.
 $ helm package docs/examples/alpine/
 $ mkdir fantastic-charts
 $ mv alpine-0.1.0.tgz fantastic-charts/
-$ helm repo index fantastic-charts --url https://fantastic-charts.storage.googleapis.com
+$ helm repo index --url https://fantastic-charts.storage.googleapis.com fantastic-charts
 ```
 
 The last command takes the path of the local directory that you just created and