Required status check from repo settings are not taken into account

## Problem Description

### What is actually happening
I have a suborg and repo setting file. The suborg settings file contains settings that the repo setting is supposed to override.

suborg setting:
```
suborgrepos:
- my-*

branches:
- name: default
protection:
required_pull_request_reviews:
required_approving_review_count: 1
dismiss_stale_reviews: true
require_code_owner_reviews: true
dismissal_restrictions: {}
bypass_pull_request_allowances:
users: []
teams: []
apps:
- azure-pipelines
require_last_push_approval: false
required_status_checks:
strict: true
checks:
- context: validate
enforce_admins: false
required_linear_history: true
allow_force_pushes: false
allow_deletions: false
block_creations: true
required_conversation_resolution: true
allow_fork_syncing: false
restrictions: null
```

repo setting my-repo.yml:
```
branches:
- name: default
protection:
required_status_checks:
strict: true
checks: []
```

### What is the expected behavior
I expect that the status check on `my-repo` is empty since `checks` is set to an empty list.

### Error output, if available
Unfortunately the status check still contains the `validate` check in the branch protections.

## Context

### Are you using the hosted instance of probot/settings or running your own?
Hosted

### If running your own instance, are you using it with github.com or GitHub Enterprise?
GitHub.com

#### Version of probot/settings
latest
#### Version of GitHub Enterprise