chore(deps): bump cachix/install-nix-action from 30 to 31 (#149)

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)
- [Changelog](https://github.com/cachix/install-nix-action/blob/master/RELEASE.md)
- [Commits](cachix/install-nix-action@v30...v31)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-version: '31'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/formal-verification.yml

@@ -151,7 +151,7 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Install Nix
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixos-unstable
 

.github/workflows/release.yml

@@ -160,7 +160,7 @@ jobs:
     # Nix is required for rules_rocq_rust toolchain registered in MODULE.bazel
     # (Bazel evaluates all toolchains during loading, even for non-Rocq builds)
     - name: Install Nix
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixos-unstable
 

.github/workflows/rust.yml

@@ -70,7 +70,7 @@ jobs:
     # Bazel setup and builds
     - name: Install Nix
       if: matrix.build-system == 'bazel'
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixos-unstable