Bump plek from 2.1.0 to 2.1.1
Bump plek from 2.1.0 to 2.1.1

Bumps [plek](https://github.com/alphagov/plek) from 2.1.0 to 2.1.1.
- [Changelog](https://github.com/alphagov/plek/blob/master/CHANGELOG.md)
- [Commits](https://github.com/alphagov/plek/compare/v2.1.0...v2.1.1)
alphagov/transition,alphagov/transition,alphagov/transition