Bump strata-bridge-primitives from 921a813 to 6c3cb2f in /backend

Bumps [strata-bridge-primitives](https://github.com/alpenlabs/strata-bridge) from `921a813` to `6c3cb2f`.
- [Commits](alpenlabs/strata-bridge@921a813...6c3cb2f)

---
updated-dependencies:
- dependency-name: strata-bridge-primitives
  dependency-version: 6c3cb2fb4a3579020f95c0640b5b7e211aa1d1ac
  dependency-type: direct:production
...

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