build(deps): bump actions/checkout from v2.3.1 to v2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from v2.3.1 to v2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2.3.1...5a4ac90)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
         - nixos
         - tux-nixos
     steps:
-    - uses: actions/checkout@v2.3.1
+    - uses: actions/checkout@v2.3.4
       with:
         fetch-depth: 0 # Nix Flakes doesn't work on shallow clones
     - uses: cachix/install-nix-action@v12