Fix extraContainers indentation (#14899)

Reverts indentation change from https://github.com/helm/charts/pull/14306
so that `extraContainers` can be overridden like this

```
server:
  extraContainers: |
    - name: extra-container
      image: "docker.io/some/image:1.0"
      pullPolicy: IfNotPresent
```

Signed-off-by: Jonas Arneberg <jonas.arneberg@gmail.com>

stable/drone/Chart.yaml

@@ -2,7 +2,7 @@ apiVersion: v1
 name: drone
 home: https://drone.io/
 icon: https://drone.io/apple-touch-icon.png
-version: 2.0.2
+version: 2.0.3
 appVersion: 1.1.0
 description: Drone is a Continuous Delivery system built on container technology
 keywords:

stable/drone/templates/deployment-server.yaml

@@ -117,7 +117,7 @@ spec:
         - name: data
           mountPath: /var/lib/drone
 {{- with .Values.server.extraContainers }}
-{{ tpl . $ | indent 10 }}
+{{ tpl . $ | indent 6 }}
 {{- end }}
       volumes:
       {{ if eq .Values.sourceControl.provider "bitbucketServer" -}}