grafana: Increase readiness probe timeout

Sometimes, Grafana gets pretty slow, especially when it's running on one
of the Raspberry Pi nodes.  When this happens, the health check may take
longer than the default timeout of 1 second to respond.  This then marks
the pod as unhealthy, even though it's still working.

grafana/grafana.yaml

@@ -60,6 +60,7 @@ spec:
             port: http
             path: /api/health
           periodSeconds: 60
+          timeoutSeconds: 5
         startupProbe:
           <<: *probe
           periodSeconds: 1