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

(cherry picked from commit c42083a33950be6ee9f822c6d0de3c3a79d1f51b)

Conflicts:
	models/repo/repo_list_test.go
	tests/integration/api_nodeinfo_test.go
	tests/integration/api_repo_test.go
	shared fixture counts

models/issues/issue_test.go

@@ -381,7 +381,7 @@ func TestCountIssues(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 	count, err := issues_model.CountIssues(db.DefaultContext, &issues_model.IssuesOptions{})
 	assert.NoError(t, err)
-	assert.EqualValues(t, 20, count)
+	assert.EqualValues(t, 22, count)
 }
 
 func TestIssueLoadAttributes(t *testing.T) {