Task identity links not updated when deleting candidates

**Describe the bug**
When the candidates of a task are modified, specifically deleted by calling org.flowable.task.service.delegate.DelegateTask#deleteCandidateUser, the list of identity links in the task object is not updated. What's worse, that persists through different task listeners.

**Expected behavior**
After calling org.flowable.task.service.delegate.DelegateTask#deleteCandidateUser I expect that org.flowable.task.service.delegate.DelegateTask#getCandidates will reflect the changes.

**Code**
org.flowable.task.service.delegate.DelegateTask#deleteCandidateUser
org.flowable.task.service.delegate.DelegateTask#getCandidates
org.flowable.task.service.impl.persistence.entity.TaskEntityImpl#getIdentityLinks

**Additional context**
Flowable version 7.1.0.27

Inizia con DelegateTask#deleteCandidateUser e DelegateTask#getCandidates, quindi traccia come viene mantenuto TaskEntityImpl#getIdentityLinks attraverso i task listener. Riproduci l’eliminazione del candidato usando Flowable 7.1.0.27 e verifica che getCandidates rifletta coerentemente l’eliminazione dopo l’esecuzione dei listener successivi.

Scritto dal modello di indicizzazione a partire dal testo della issue.