Removes Hassio external storage page (#9737)

* No longer valid

https://github.com/home-assistant/home-assistant.io/issues/9712

* Remove External storage

source/_includes/asides/hassio_navigation.html

@@ -17,7 +17,6 @@
         <ul>
           <li>{% active_link /hassio/commandline/ Command line %}</li>
           <li>{% active_link /hassio/zwave/ Z-Wave %}</li>
-          <li>{% active_link /hassio/external_storage/ External storage %}</li>
           <li>{% active_link /hassio/run_local/ Execute local things %}</li>
           <li>{% active_link /hassio/enable_i2c/ Enable I2C %}</li>
         </ul>

source/hassio/external_storage.markdown

@@ -1,21 +0,0 @@
----
-layout: page
-title: "External device"
-description: "How to map external device on Hass.io."
-date: 2017-04-30 13:28
-sidebar: true
-comments: false
-sharing: true
-footer: true
----
-
-### {% linkable_title ResinOS / Generic %}
-
-Map the USB drive into add-on with `devices` options. If you need it on multiple add-ons, you can use the `/share` folder which is accessible from various add-ons.
-It is also possible to create an add-on that only mounts stuff to `share`.
-
-You can format the USB device with multiple volumes and map it to a specific add-on.
-
-### {% linkable_title Generic %}
-
-The `share` defaults to `/usr/share/hassio/share` so you can mount your volumes into this folder.