build(deps): bump cachix/install-nix-action from 18 to 19

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 18 to 19.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v18...v19)

---
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/release-tip.yml

@@ -23,7 +23,7 @@ jobs:
         fetch-depth: 0
 
     # Install Nix and use that so our environment matches exactly.
-    - uses: cachix/install-nix-action@v18
+    - uses: cachix/install-nix-action@v19
       with:
         nix_path: nixpkgs=channel:nixos-unstable
 

.github/workflows/test.yml

@@ -31,7 +31,7 @@ jobs:
         fetch-depth: 0
 
     # Install Nix and use that to run our tests so our environment matches exactly.
-    - uses: cachix/install-nix-action@v18
+    - uses: cachix/install-nix-action@v19
       with:
         nix_path: nixpkgs=channel:nixos-unstable
 
@@ -53,7 +53,7 @@ jobs:
         fetch-depth: 0
 
     # Install Nix and use that to run our tests so our environment matches exactly.
-    - uses: cachix/install-nix-action@v18
+    - uses: cachix/install-nix-action@v19
       with:
         nix_path: nixpkgs=channel:nixos-unstable