Fix: Return primary email address, not the first

When a user has multiple email addresses, the first doesn't necessarily have to be the primary email address.

```json
[
    {
        "email": "john@example.org",
        "verified": true,
        "primary": false
    },
    {
        "email": "john.doe@example.com",
        "verified": true,
        "primary": true
    }
]
```

This PR fixes `Hybrid_Providers_GitHub::getUserProfile()` by iterating over the array of email addresses to find the one that is the primary email address.