Precedence order not working as expected for arrays in branch policy

## Problem Description

As per the README - The precedence order for settings file is `repository > suborg > org` (.github/repos/.yml > .github/suborgs/.yml > .github/settings.yml

However, when defining branch policies at both the suborganization and repository levels, policies that require array inputs are merged rather than being overridden.

### What is actually happening

**suborg/default.bpr.yml**
```
suborgrepos:
- '*'

branches:
- name: default
protection:
required_pull_request_reviews: null
required_status_checks: null
enforce_admins: false
restrictions:
apps: ['app-01', 'app-02']
users: ['user-01']
teams: []
```

**repos/repo.yml**
```

branches:
- name: default
protection:
required_pull_request_reviews: null
required_status_checks: null
enforce_admins: true
restrictions:
apps: ['app-03']
users: ['user-02']
teams: []
```

Properties with boolean or string input types are functioning as expected, and the values defined in the repo.yml file are being correctly applied. However, properties with array input types are being merged instead of being overridden.

For instance, the restriction being applied is:

```
restrictions:
apps: ['app-01', 'app-02', 'app-03']
users: ['user-01', 'user-02']
teams: []
```

### What is the expected behavior

Only the apps and users defined in the repo.yml should be applied, while the apps and users defined the sub-org level should be ignored.
```
restrictions:
apps: ['app-03']
users: ['user-02']
teams: []
```

### Error output, if available

NA

## Context

### Are you using the hosted instance of probot/settings or running your own?
Running Safe Settings via Github Actions

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

#### Version of probot/settings
2.1.14

#### Version of GitHub Enterprise
NA