github-actions: bump cachix/cachix-action from 14 to 15

Bumps [cachix/cachix-action](https://github.com/cachix/cachix-action) from 14 to 15.
- [Release notes](https://github.com/cachix/cachix-action/releases)
- [Commits](cachix/cachix-action@v14...v15)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/devenv.yaml

@@ -68,7 +68,7 @@ jobs:
 
       - id: cachix
         name: "Enable Cachix ❄️"
-        uses: cachix/cachix-action@v14
+        uses: cachix/cachix-action@v15
         with:
           name: ${{ secrets.CACHIX_CACHE_NAME }}
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}

.github/workflows/nix-container.yaml

@@ -118,7 +118,7 @@ jobs:
 
       - id: cachix
         name: "Enable Cachix ❄️"
-        uses: cachix/cachix-action@v14
+        uses: cachix/cachix-action@v15
         with:
           name: ${{ secrets.CACHIX_CACHE_NAME }}
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}

.github/workflows/nix-flake-check.yaml

@@ -37,7 +37,7 @@ jobs:
 
       - id: cachix
         name: "Enable Cachix ❄️"
-        uses: cachix/cachix-action@v14
+        uses: cachix/cachix-action@v15
         with:
           name: ${{ secrets.CACHIX_CACHE_NAME }}
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}

.github/workflows/nix-flake-update.yaml

@@ -30,7 +30,7 @@ jobs:
 
       - id: cachix
         name: "Enable Cachix ❄️"
-        uses: cachix/cachix-action@v14
+        uses: cachix/cachix-action@v15
         with:
           name: ${{ secrets.CACHIX_CACHE_NAME }}
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}