build(deps-dev): update @vuepress/theme-default requirement
build(deps-dev): update @vuepress/theme-default requirement

Updates the requirements on [@vuepress/theme-default](https://github.com/vuejs/vuepress/tree/HEAD/packages/@vuepress/theme-default) to permit the latest version.
- [Release notes](https://github.com/vuejs/vuepress/releases)
- [Changelog](https://github.com/vuejs/vuepress/blob/master/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vuepress/commits/v1.4.0/packages/@vuepress/theme-default)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
FullHuman/purgecss,FullHuman/purgecss,FullHuman/purgecss,FullHuman/purgecss