Remove NGINX DefaultBackend from tests
Removes testing for (non)existence of NIGNX DefaultBackend components.
In gitlab-org/charts/gitlab!2686 (merged), the default upstream value was respected (disabled) rather than manually enabling it.
Note that the defaultBackend ServiceAccount settings remain so that if the component is enabled, the desired security settings are maintained.
Closes #819 (closed)
Changelog: other
Edited by Mitchell Nielsen