[cloud] Redirect the user when leaving organization

Created by: kopancek

When leaving an org, the user is no longer a member of the organization so it does not make sense to render the organization members list to them anymore, as it will result with an error.

Instead we should redirect to user settings, which this change achieves.

Related: https://sourcegraph.atlassian.net/browse/CLOUD-348

Test plan

Tested locally. We do not have integration or E2E tests for this functionality, so testing manually is the only way. This feature is behind a feature flag, so no impact expected to the customers.

App preview:

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