chore(nix): bump rust-overlay from adf987c to bc83d66

Bumps [rust-overlay](https://github.com/oxalica/rust-overlay) from `adf987c` to `bc83d66`.
- [Commits](oxalica/rust-overlay@adf987c...bc83d66)

---
updated-dependencies:
- dependency-name: rust-overlay
  dependency-version: bc83d66023d19fb301ee98772643b24b6129ef48
  dependency-type: direct:production
...

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Author: dependabot[bot]