build(deps-dev): bump scratch-l10n

Bumps [scratch-l10n](https://github.com/LLK/scratch-l10n) from 3.9.20200609200912 to 3.9.20200615152937.
- [Release notes](https://github.com/LLK/scratch-l10n/releases)
- [Commits](https://github.com/LLK/scratch-l10n/compare/3.9.20200609200912...3.9.20200615152937

)

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