Bump serialize-javascript from 1.6.1 to 2.1.1 in /backend (#1831)
Bump serialize-javascript from 1.6.1 to 2.1.1 in /backend (#1831)

Bumps [serialize-javascript](https://github.com/yahoo/serialize-javascript) from 1.6.1 to 2.1.1.
- [Release notes](https://github.com/yahoo/serialize-javascript/releases)
- [Commits](https://github.com/yahoo/serialize-javascript/compare/v1.6.1...v2.1.1)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
3drepo/3drepo.io,3drepo/3drepo.io,3drepo/3drepo.io,3drepo/3drepo.io,3drepo/3drepo.io,3drepo/3drepo.io