build(deps): bump contentful-management from 5.19.0 to 5.21.1

Bumps [contentful-management](https://github.com/contentful/contentful-management.js) from 5.19.0 to 5.21.1.
- [Release notes](https://github.com/contentful/contentful-management.js/releases)
- [Commits](contentful/contentful-management.js@v5.19.0...v5.21.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>