Remove the admin field from the config object

[coltonhurst]

Type of change

- [ ] Bug fix
- [ ] New feature development
- [ ] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [ ] Build/deploy pipeline (DevOps)
- [x] Other

Objective

We added the admin url in the config object as part of the new work adding a config endpoint to the API, but in hindsight we do not want to expose this url.

Code changes

• ConfigResponseModel.cs: Removed the admin field in the EnvironmentConfigResponseModel and stopped setting it in the ConfigResponseModel constructor

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