Update toggle_use_case (#902)
Update toggle_use_case (#902)

* Update toggle_use_case

`permanent` is not a valid setting for this.  The use cases are defined here: https://github.com/edx/edx-toggles/blob/master/docs/how_to/documenting_new_feature_toggles.rst#toggle_use_cases.

Based on the use case definitions, it looks like this most closely matches the "Open edX Option" case:

| When a team implements a feature that they do not expect to be adopted by all Open edX instances, they may introduce a toggle to gate the feature.
edx/credentials,edx/credentials,edx/credentials,edx/credentials