build(deps): bump dimod from 0.12.20 to 0.12.21

Bumps [dimod](https://github.com/dwavesystems/dimod) from 0.12.20 to 0.12.21.
- [Release notes](https://github.com/dwavesystems/dimod/releases)
- [Commits](dwavesystems/dimod@0.12.20...0.12.21)

---
updated-dependencies:
- dependency-name: dimod
  dependency-version: 0.12.21
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]