Bump graphql from 16.6.0 to 16.8.1 in /backend

Bumps [graphql](https://github.com/graphql/graphql-js) from 16.6.0 to 16.8.1.
- [Release notes](https://github.com/graphql/graphql-js/releases)
- [Commits](graphql/graphql-js@v16.6.0...v16.8.1)

---
updated-dependencies:
- dependency-name: graphql
  dependency-type: indirect
...

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