mattermost-team-edition chart - Error in documentation

[cade-thomas]

Mattermost-team-edition helm chart documentation claim's configJSON is supported by the chart and links a version of the values file 6 years old https://github.com/helm/charts/blob/master/stable/mattermost-team-edition/values.yaml

This should be removed as the modern version of the chart only supports config.x and not no longer supports configJSON

[cade-thomas]

ConfigJSON is also referenced here https://github.com/mattermost/mattermost-helm/tree/master/charts/mattermost-team-edition#example-configuration

As seen by https://github.com/mattermost/mattermost-helm/blob/master/charts/mattermost-team-edition/templates/secret-config.yaml this is no longer supported

[stafot]

Feel free to propose PR with these fixes @cade-thomas