Bumps [letter_opener](https://github.com/ryanb/letter_opener) from 1.6.0 to 1.7.0. - [Release notes](https://github.com/ryanb/letter_opener/releases) - [Changelog](https://github.com/ryanb/letter_opener/blob/master/CHANGELOG.md) - [Commits](https://github.com/ryanb/letter_opener/compare/v1.6.0...v1.7.0) Signed-off-by: dependabot[bot] <support@dependabot.com>master