Change grafana provisioning.yaml indentation

This commit changes the indentation scheme used in
`ansible/roles/grafana/templates/provisioning.yaml.j2` to the commonly
used pattern of two whitespaces.

Change-Id: I2f9d34930ed06aa2e63f7cc28bfdda7046fc3e67

ansible/roles/grafana/templates/provisioning.yaml.j2

@@ -2,10 +2,10 @@
 apiVersion: 1
 
 providers:
- - name: 'default'
-   orgId: 1
-   folder: ''
-   folderUid: ''
-   type: file
-   options:
-     path: /var/lib/grafana/dashboards
+  - name: 'default'
+    orgId: 1
+    folder: ''
+    folderUid: ''
+    type: file
+    options:
+      path: /var/lib/grafana/dashboards