[Missions] Mission.isApproved() is ambiguous and should be removed

[JoaoRoxoNeves]

expenditures/expenditure-tracking/src/main/java/module/mission/domain/Mission.java

Line 344 in bb40f13

public boolean isApproved() {

As an API method, the logic that this method implements is not clear.
In the context of a MissionProcess, the "approval" keyword is used to represent the first step of approval by the mission's responsible.
That logic is already implemented in isApprovedByMissionResponsible()

The method isApproved() should be removed, and any references to it should be refactored.