Update spinnaker-service-monitor.yaml

[lyzhang1999]

The namespaceSelector should be a child of spec, not selector

[spinnakerbot]

The following commits need their title changed:

• ea176ef: Update spinnaker-service-monitor.yaml

Please format your commit title into the form:

<type>(<scope>): <subject>, e.g. fix(kubernetes): address NPE in status check

This allows us to easily generate changelogs & determine semantic version numbers when cutting releases. You can read more about commit conventions here.