Transfer API Subscription to published plan not working as expected

[exalate-issue-sync]

Describe the bug :

When using their API, when we try to use the transfer subscription option in APIM Console, it dissables the first two plans and the last two are only available, but when doing the same thing via the rest API it seems to allow subscription transfer to all plans regardless. As per the dev team apparently this issue has already been fixed in the past, but it seems the change was not properly applied on 3.20.x gravitee-io/gravitee-api-management#4244

To Reproduce :

Steps to reproduce the behaviour:

1. Import their API
2. Go to applications, create an application
3. Subscribe the application to the 'default' plan for example
4. See error

Desktop :

• Environment: [3.20.10]

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