PWB: Set launcher.useTemplates: true by default

[tnederlof]

This PR sets the default to launcher.useTemplates: true in the Workbench chart. This bumps the chart a minor version to 0.9.0 since it could be breaking if someone is using job-json-overrides because both cannot be set simultaneously. There is a check in the helm chart that will error if both job-json-overrides and launcher.useTemplates=true are defined, this PR adds to that error to note the chart version where this default was changed.

This being false by default is the most common root cause of customer issues we see in the field because without it many other chart defaults and examples Posit puts out will subtly not be applied (for example, session changes to pip.conf, imagePullSecrets, mounting storage to sessions etc.).

Historically before launcher.templateValues existed setting job-json-overrides was the way to customize jobs and it is still what is documented in our helm chart README. This PR removes the job-json-overrides language from the README and instead instructs users to use launcher.templateValues to customize the job templates.

Also worth noting that the Connect chart sets this default to true.

[GCRev]

LGTM and we hope people read the changelog

[tnederlof]

Hopefully there is enough detail
In the error message for people to have the action steps to resolve!