document changes in spentTime behaviour

doc/apiv3.apib

@@ -21,6 +21,9 @@ already present in the core API.
 | id          | Budget id                                   | Integer     | x > 0       | READ                 |                             |
 | subject     | Budget name                                 | String      | not empty   | READ                 |                             |
 
+`spentTime` has its visibility condition changed! It is now only visible when the client is either allowed to view time entries, or if
+he is allowed to see his own time entries in projects where the costs module is enabled.
+
 *Note: Further properties of budgets might be added at a future date, however they will require the view budget permission to be displayed.*
 
 ## Budget [/api/v3/budgets/{id}]