### Steps to reproduce

1. Go to the notification center and have mulitple work packages listed

2. Open the first work package on the relations tab

3. Add a child wp (chose one that is not listed on the page already)

4. Go to the any other workpackage notification

5. open the relations tab

6. Add the child that you added before now to this WorkPackage

7. Observe the counter of the relations tab header

1. alternatively: watch the network tab in the browser console


### What is the buggy behavior?

* The counter is updated Begin of the insertiontwiceEnd of the insertion Begin of the deletion multiple times, depending on the position of the notification itemEnd of the deletion

* Begin of the deletion So if it is the third item, it is updated three times

* End of the deletion Each call, has a different work package ID assigned Begin of the insertion(first the IDEnd of the insertion Begin of the deletion (thoseEnd of the deletion of the Begin of the insertionold WP, the second request has the new WP id assigned)

* thisEnd of the insertion Begin of the deletion other notification items) whichEnd of the deletion causes the counter to flicker as it shows the number of the Begin of the insertionoldEnd of the insertion Begin of the deletion otherEnd of the deletion WorkPackages before the correct one is rendered.

* Unfortunately, that can only barely be seen, but I strongly assume that `rspec ./spec/features/work_packages/details/relations/hierarchy_spec.rb:155` flickered because of that.


### What is the expected behavior?

1. Only the counter for the actual WP should be loaded, not all previous WP as well


### Begin of the insertion<img class="op-uc-image op-uc-image_inline" src="/api/v3/attachments/243314/content">

<br>

End of the insertion Begin of the deletion

End of the deletion ### Environment information

**OpenProject version**

_15.1_

**Browser**

* [x] Chrome
* [ ] Firefox
* [ ] Safari
* [ ] Mobile Safari
* [ ] Other (please specify)

**Operating System**

* [ ] Windows
* [x] Mac OS X
* [ ] Mobile iOS
* [ ] Mobile Android
* [ ] Linux (please specify distro)
* [ ] Chrome OS
* [ ] Other (please specify)

**Language**

_German_