Bump cachix/install-nix-action from 30 to 31

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 30 to 31.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@v30...v31)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/cache.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/[email protected]
 
       - name: "Install Nix️"
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@v31
 
       - name: "Install Cachix️"
         uses: cachix/cachix-action@v15

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/[email protected]
 
       - name: "Install Nix️"
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@v31
 
       - name: "Install Cachix️"
         uses: cachix/cachix-action@v15