Bump terser from 5.12.1 to 5.14.2 in /backend

Bumps [terser](https://github.com/terser/terser) from 5.12.1 to 5.14.2. - [Release notes](https://github.com/terser/terser/releases) - [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md) - [Commits](https://github.com/terser/terser/commits) --- updated-dependencies: - dependency-name: terser dependency-type: indirect ... Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]