Move "User Guide" up in the sidebar

So that it is above "Accessing the Cluster" article which describes
more advanced topics and does not look coherent when it is read
linearly.

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

_data/guides.yml

@@ -5,6 +5,8 @@ toc:
 
 - docs/whatisk8s.md
 
+- docs/user-guide/index.md
+
 - title: Accessing the Cluster
   section:
   - docs/user-guide/prereqs.md
@@ -12,8 +14,6 @@ toc:
   - docs/user-guide/sharing-clusters.md
   - docs/user-guide/kubeconfig-file.md
 
-- docs/user-guide/index.md
-
 - docs/user-guide/ui.md
 
 - title: Workload Deployment and Management