chore(deps): bump cachix/install-nix-action from 25 to 26

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 25 to 26.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v25...v26)

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

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

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ${{ matrix.runs-on }}
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v25
+      - uses: cachix/install-nix-action@v26
       - uses: ./
       - run: actionlint
       - run: shellcheck nix-develop-gha.sh

nix-develop-gha.sh

@@ -26,7 +26,7 @@ while IFS='=' read -r -d '' n v; do
 		continue
 	fi
 	if (("$(wc -l <<<"$v")" > 1)); then
-		delimiter=BzcqNQnW6x7hfGlLbvCyDlvD
+		delimiter=$(openssl rand -base64 18)
 		if contains "$delimiter" "$v"; then
 			echo "Environment variable $n contains randomly generated string $delimiter, file an issue and buy a lottery ticket."
 			exit 1