Should we delete obsolete `PerformanceTiming` interface

[shubhamg13]

8.1. The PerformanceTiming interface

This results in wrong impression on WPT Score. As new browsers won't implement these obsolete specs.

Since the Specs marks it obsolete. So, we can do either things or any other suggestions.

• Either delete the contents from existing file.
• Segregate it into 2 separate files navigation-timing and navigation-timing-2
• Maybe modify reffy to not extract obselete interface

[shubhamg13]

cc: @xiaochengh