Bump cachix/install-nix-action from v10 to v11 (#9)

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from v10 to v11.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v10...95a8068e317b8def9482980abe762f36c77ccc99)

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

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

.github/workflows/nix.yml

@@ -9,7 +9,7 @@ jobs:
         with:
           # Nix Flakes doesn't work on shallow clones
           fetch-depth: 0
-      - uses: cachix/install-nix-action@v10
+      - uses: cachix/install-nix-action@v11
         with:
           install_url: https://github.com/numtide/nix-flakes-installer/releases/download/nix-2.4pre20200618_377345e/install
       - run: echo "experimental-features = nix-command flakes" | sudo tee -a /etc/nix/nix.conf