build(deps): bump actions/checkout from 3 to 4 (#2)

Bump https://github.com/actions/checkout from 3 to 4.

References:

- https://github.com/actions/checkout/blob/main/CHANGELOG.md
- actions/checkout@v3...v4
- https://github.com/actions/checkout/releases

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/nix_flake_check.yml

@@ -7,7 +7,7 @@ jobs:
   nix-flake-check:
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@v9
       - uses: DeterminateSystems/magic-nix-cache-action@v2
       - run: nix flake check