Update Policy-based auth instructions to use cURL

### Description

#33094 removed Postman per security updates. The instructions for testing the app need to be update.

Extract the commands from the `ContosoAPI.collection.json` file and use them to construct cURL commands to test the app.

### Page URL

https://learn.microsoft.com/en-us/aspnet/core/security/authorization/policies?view=aspnetcore-8.0&branch=pr-en-us-33094

### Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/security/authorization/policies.md

### Document ID

7089b376-949f-c1c6-c37a-5d8cc7ecf104

### Article author

@Rick-Anderson