Bump vue and vue-template-compiler in /apps/updatenotification

Bumps [vue](https://github.com/vuejs/vue) and [vue-template-compiler](https://github.com/vuejs/vue). These dependencies needed to be updated together.

Updates `vue` from 2.6.2 to 2.6.4
- [Release notes](https://github.com/vuejs/vue/releases)
- [Commits](https://github.com/vuejs/vue/compare/v2.6.2...v2.6.4)

Updates `vue-template-compiler` from 2.6.2 to 2.6.4
- [Release notes](https://github.com/vuejs/vue/releases)
- [Commits](https://github.com/vuejs/vue/compare/v2.6.2...v2.6.4

)

Signed-off-by: dependabot[bot] <support@dependabot.com>
Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>