Update upgrade-anbox.md

Fix version for stable channels

howto/update/upgrade-anbox.md

@@ -103,10 +103,10 @@ If you don't run any of the services in a high availability configuration, upgra
 
 To upgrade all charms, run the following commands:
 
-    juju refresh --channel=1.20/stable anbox-cloud-dashboard
-    juju refresh --channel=1.20/stable anbox-stream-gateway
-    juju refresh --channel=1.20/stable anbox-stream-agent
-    juju refresh --channel=1.20/stable coturn
+    juju refresh --channel=1.22/stable anbox-cloud-dashboard
+    juju refresh --channel=1.22/stable anbox-stream-gateway
+    juju refresh --channel=1.22/stable anbox-stream-agent
+    juju refresh --channel=1.22/stable coturn
     juju refresh --channel=latest/stable nats
 
 [note type="information" status="Note"]
@@ -177,4 +177,4 @@ You can check for the status of an existing application by running:
 
     amc application show <application id or name>
 
-In case automatic updates are disabled for applications, AMS cannot update the application. See [Configure automatic application updates](https://discourse.ubuntu.com/t/24201#configure-automatic-application-updates-3) to enable automatic updates or to manually update the applications.
+In case automatic updates are disabled for applications, AMS cannot update the application. See [Configure automatic application updates](https://discourse.ubuntu.com/t/24201#configure-automatic-application-updates-3) to enable automatic updates or to manually update the applications.