Updates outdated Docs site URLs

[ember-stevens]

Requirements

• [ n/a ] I have added test coverage for new or changed functionality
• [ X ] I have followed the repository's pull request submission guidelines
• [ n/a ] I have validated my changes against all supported platform versions

Related issues

N/A

Describe the solution you've provided

Updated old URLs linking to the old docs site to current URLs for the current docs site.

Describe alternatives you've considered

N/A

Additional context

Some docs site URLs changed in 2020 when we changed hosting platforms and there have been IA changes since.