Add Steps: Remove Getting Started panel from Grafana

[siggy]

#245 fixed a build issue in the Add Steps demo by upgrading Grafana. That version bump introduced a "Getting Started" panel in the Grafana dashboard, which should be removed.

Background

Newer versions of Grafana include a "Getting Started" panel that should be disabled for our demo:

Proposal

Change the anonymous org role from Admin to Editor:

diff --git a/add-steps/docker-compose.yml b/add-steps/docker-compose.yml
index b391b36..5573f71 100644
--- a/add-steps/docker-compose.yml
+++ b/add-steps/docker-compose.yml
@@ -149,7 +149,7 @@ services:
       - 3000:3000
     environment:
       - GF_AUTH_ANONYMOUS_ENABLED=true
-      - GF_AUTH_ANONYMOUS_ORG_ROLE=Admin
+      - GF_AUTH_ANONYMOUS_ORG_ROLE=Editor

   baseline_slow_cooker:
     image: buoyantio/slow_cooker:1.1.0-golang1.8rc2

Note that this breaks our bootstrap.sh script because we can no longer add datasources via the Grafana HTTP API:

$ curl http://localhost:3000/api/datasources
{"message":"Permission denied"}

To address this, add the Prometheus datasource via Datasource provisioning rather than via API. For example: https://github.com/linkerd/linkerd-viz/blob/c6b4f2baff880ac5c093b6beaec1d42140ce2a48/linkerd-viz#L45-L61

Also bump the Kubernetes version to Grafana 5.4.3: https://github.com/linkerd/linkerd-examples/blob/d50b911dec4d811a188f66979c45edc1fdb9a90e/add-steps/k8s/add-steps.yml#L918