[BUG] Unsharing content shared by other manager

## Describe the bug

Two managers of the same space. Manager 1 shares an item with any user. Manager 2 tries to unshare. It returns `500 internal Server Error`. It's not the expected response.

## Steps to reproduce

(using client)

1. Add two managers to the same space: `Manager1` and `Manager2`
2. `Manager1` shares file1.txt with any user of the platform. Any permission, not relevant
3. `Manager2` , who also has sharing permissions, does not like that and tries to unshare file1.txt`

## Actual behavior

Server responses with `500 Internal Server Error`

Request:

`DELETE https:///graph/v1beta1/drives//items//permissions/`

response payload:

```
{
"error": {
"code": "generalException",
"innererror": {
"date": "2026-09-04T11:33:45Z",
"request-id": "07F0F940-65A1-4514-96B9-7206AB3D836C"
},
"message": "error removing share"
}
}
```

## Expected behavior

Not clear. Is it allowed to remove a "share with user" by other manager in a custom space? Links do.

Anyway, the response should be `4xx` and not `500`

## Setup