chore(deps): update determinatesystems/nix-installer-action action to v21

Author: renovate[bot]

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
 
       - name: Install Nix
         if: ${{ matrix.use-nix }}
-        uses: DeterminateSystems/nix-installer-action@v20
+        uses: DeterminateSystems/nix-installer-action@v21
 
       - name: Setup Nix cache
         if: ${{ matrix.use-nix }}
@@ -55,7 +55,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v20
+        uses: DeterminateSystems/nix-installer-action@v21
 
       - name: Setup Nix cache
         uses: DeterminateSystems/magic-nix-cache-action@v13

.github/workflows/clippy.yml

@@ -28,7 +28,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v20
+        uses: DeterminateSystems/nix-installer-action@v21
 
       - name: Setup Nix cache
         uses: DeterminateSystems/magic-nix-cache-action@v13

.github/workflows/docker.yml

@@ -22,7 +22,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v20
+        uses: DeterminateSystems/nix-installer-action@v21
 
       - name: Setup Nix cache
         uses: DeterminateSystems/magic-nix-cache-action@v13

.github/workflows/update-flake.yml

@@ -20,7 +20,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v20
+        uses: DeterminateSystems/nix-installer-action@v21
 
       - name: Update flake.lock
         id: update