fix: get_team_attribute_by_quota_resource always return list

[patricio-posthog]

Problem

https://posthog.sentry.io/issues/6185491305/?alert_rule_id=14968077&alert_type=issue&notification_uuid=e63c0bfc-9977-4b8b-8b43-2a2c98ed4fa8&project=1899813&referrer=slack

In get_team_attribute_by_quota_resource, if the list team_tokens is empty, instead of returning the empty list, we returned None. That breaks sync_org_quota_limits that expects a list when calling that function.

Changes

We always return a list, even an empty list.

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Does this work well for both Cloud and self-hosted?

Only for cloud since it's billing.

How did you test this code?

Current tests are passing.

[raquelmsmith]

If we want to make sure this is always this way, should we add a test?

[patricio-posthog]

If we want to make sure this is always this way, should we add a test?

You're right, I'll add a test for this.