Bump webpack from 4.14.0 to 4.15.1 in /apps/updatenotification

Bumps [webpack](https://github.com/webpack/webpack) from 4.14.0 to 4.15.1.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/compare/v4.14.0...v4.15.1

)

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