v2.1.0: Prevent "best practice" landmark rules from generating failures (#407)
#### Pull request checklist
- [x] Addresses an existing issue: Fixes #390
- [x] **N/A** Added relevant unit test for your changes. (`npm run test`)
- [x] Verified code coverage for the changes made. Check coverage report at: `<rootDir>/test-results/unit/coverage`
- [x] Ran precheckin (`npm run precheckin`)
- [x] **N/A** Added screenshots/GIFs for UI changes.
#### Description of changes
This marks the rules noted in #390 as "BestPractice", which practically speaking disables them from consideration by the extension (the `RuleSifter` class omits them).
#### Notes for reviewers
Verified against the repro site noted in #390 that this resolves the unique-landmark violations there and cooperates with loading persisted assessment state that includes the removed requirements.