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/ci.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: "${{ matrix.os }}"
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v30
+      - uses: cachix/install-nix-action@v31
       - uses: cachix/cachix-action@v16
         with:
           name: dschrempf-nix-script
@@ -31,7 +31,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v30
+      - uses: cachix/install-nix-action@v31
       - uses: cachix/cachix-action@v16
         with:
           name: nix-script

.github/workflows/nix.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           ref: main
-      - uses: cachix/install-nix-action@v30
+      - uses: cachix/install-nix-action@v31
       - run: nix flake update
       - name: Create PR
         env: