build(deps): bump github.com/mitchellh/mapstructure from 1.3.3 to 1.4.0

Bumps [github.com/mitchellh/mapstructure](https://github.com/mitchellh/mapstructure) from 1.3.3 to 1.4.0.
- [Release notes](https://github.com/mitchellh/mapstructure/releases)
- [Changelog](https://github.com/mitchellh/mapstructure/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mitchellh/mapstructure/compare/v1.3.3...v1.4.0

)

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