Confusing UX around changing settings in GitHub integration

### Environment

SaaS (https://sentry.io/)

### Steps to Reproduce

1. Add GitHub integration to an organisation
2. Open the GitHub integration settings as a user with "Member" permissions
3. Try to change any of the settings

### Expected Result

The user is unable to change settings.

### Actual Result

As all options are "unlocked" and the user can apparently change them. However, the user gets "Failed to Save" or "Unknown error during saving" errors in the UI. These errors are all due to permissions (HTTP requests get a 403 response).

This causes confusion as users seem to be able to change settings but keep getting errors with no explanation on the cause.

### Product Area

Settings - Integrations

### Link

_No response_

### DSN

_No response_

### Version

_No response_

Start in Settings - Integrations and reproduce the GitHub integration flow as a user with Member permissions. Trace the settings save request and its HTTP 403 response in the UI; done means the permissions limitation is clear before or when the user attempts a change, rather than showing unexplained save errors.

Written by the indexing model from the issue text.