Build(deps): Bump golang.org/x/sync from 0.20.0 to 0.21.0

Bumps [golang.org/x/sync](https://github.com/golang/sync) from 0.20.0 to 0.21.0.
- [Commits](https://github.com/golang/sync/compare/v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: golang.org/x/sync
  dependency-version: 0.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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