`header.url` value is incorrect in `.github/security-insights.yml`

https://github.com/privateerproj/.github/blob/main/.github/security-insights.yml#L5

## Observed

```yaml
url: https://github.com/privateerproj/.github/blob/main/security-insights.yml
```

## Expected

```yaml
url: https://github.com/privateerproj/.github/blob/main/.github/security-insights.yml
```