[elasticsearch] Add namespace to helm test command in NOTES.txt

[mrtzgh]

• Chart version not bumped (the versions are all bumped and released at the same time)
• README.md updated with any new values or changes
• Updated template tests in ${CHART}/tests/*.py
• Updated integration tests in ${CHART}/examples/*/test/goss.yaml

Helm chart NOTES.txt was missing namespace in the test section:
before change:

LAST DEPLOYED: Mon Mar 15 21:24:35 2021
NAMESPACE: elk
STATUS: deployed
REVISION: 1
NOTES:
1. Watch all cluster members come up.
  $ kubectl get pods --namespace=elk -l app=elasticsearch-master -w
2. Test cluster health using Helm test.
  $ helm test elasticsearch

after change:

NAMESPACE: elk
STATUS: deployed
REVISION: 1
NOTES:
1. Watch all cluster members come up.
  $ kubectl get pods --namespace=elk -l app=elasticsearch-master -w
2. Test cluster health using Helm test.
  $ helm --namespace=elk test elasticsearch

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[jmlrt]

LGTM⛴

[jmlrt]

jenkins test this please