Bump more-itertools from 8.5.0 to 8.6.0

Bumps more-itertools from 8.5.0 to 8.6.0.

Release notes

Sourced from more-itertools's releases.

Version 8.6.0

See the changelog for details.

Commits

• 4d2e1db Merge pull request #472 from more-itertools/version-8.6.0
• a8d3959 Add 3.9 to tox
• 298909b Bump version: 8.5.0 → 8.6.0
• f4c5995 Doc changes for 8.6.0
• 16c626b Bring in nth_permutation
• e455b4d Add nth_permutation to docs
• ff183d2 Merge pull request #471 from N8Brooks/master
• 16a0986 removed extra whitespace on 633
• f652eab Added tests for invalid values of r
• d76f586 forgot to remove import of reduce
• Additional commits viewable in compare view