Build(ci): Bump DeterminateSystems/nix-installer-action from 20 to 21

Bumps [DeterminateSystems/nix-installer-action](https://github.com/determinatesystems/nix-installer-action) from 20 to 21.
- [Release notes](https://github.com/determinatesystems/nix-installer-action/releases)
- [Commits](DeterminateSystems/nix-installer-action@v20...v21)

---
updated-dependencies:
- dependency-name: DeterminateSystems/nix-installer-action
  dependency-version: '21'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/dev_envs.yml

@@ -18,7 +18,7 @@ jobs:
         fetch-depth: 0
 
     - name: Install Nix
-      uses: DeterminateSystems/nix-installer-action@v20
+      uses: DeterminateSystems/nix-installer-action@v21
 
     - run: nix run .# -- --version