website/integrations: Improve discord role sync policies

[Keyinator]

Details

This changes the websites integration page for discord by modifying two policies.

The new policies are easier to understand and take advantage of group attributes instead of hardcoding values (besides the guild id).

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Checklist

• [ ] Local tests pass (ak test authentik/)
• [ ] The code has been formatted (make lint-fix)

If an API change has been made

• [ ] The API schema has been updated (make gen-build)

If changes to the frontend have been made

• [ ] The code has been formatted (make web)

If applicable

• [X] The documentation has been updated
• [ ] The documentation has been formatted (make website)