Allow non-admin users to delete review requests (#29057)

Fix #14459

The following users can add/remove review requests of a PR
- the poster of the PR
- the owner or collaborators of the repository
- members with read permission on the pull requests unit

models/fixtures/org_user.yml

@@ -99,3 +99,21 @@
   uid: 5
   org_id: 36
   is_public: true
+
+-
+  id: 18
+  uid: 38
+  org_id: 41
+  is_public: true
+
+-
+  id: 19
+  uid: 39
+  org_id: 41
+  is_public: true
+
+-
+  id: 20
+  uid: 40
+  org_id: 41
+  is_public: true