chore(ci): bump flake lock actions

Multiple releases old, keep up to date.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

.github/workflows/nix-tests.yml

@@ -6,12 +6,12 @@ jobs:
   nix-flake-check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
-    - uses: cachix/install-nix-action@v27
-      with:
-        extra_nix_config: |
-          experimental-features = nix-command flakes
-          access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
-    - run: nix flake show
-    - run: nix flake check --print-build-logs
-    - run: nix build --print-build-logs
+      - uses: actions/checkout@v6
+      - uses: cachix/install-nix-action@v31
+        with:
+          extra_nix_config: |
+            experimental-features = nix-command flakes
+            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+      - run: nix flake show
+      - run: nix flake check --print-build-logs
+      - run: nix build --print-build-logs