Bump DeterminateSystems/update-flake-lock from 28 to 29

Bumps [DeterminateSystems/update-flake-lock](https://github.com/determinatesystems/update-flake-lock) from 28 to 29.
- [Release notes](https://github.com/determinatesystems/update-flake-lock/releases)
- [Commits](https://github.com/determinatesystems/update-flake-lock/compare/v28...v29)

---
updated-dependencies:
- dependency-name: DeterminateSystems/update-flake-lock
  dependency-version: '29'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/update.yml

@@ -22,7 +22,7 @@ jobs:
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
           extraPullNames: rstats-on-nix, nix-community
       - name: Update flake.lock
-        uses: DeterminateSystems/update-flake-lock@v28
+        uses: DeterminateSystems/update-flake-lock@v29
         with:
           token: ${{ secrets.GH_TOKEN }}
           branch: update