workflows: update cargo dependencies correctly (#37)

.github/workflows/build_nix.yml

@@ -3,21 +3,15 @@ on:
   pull_request:
   push:
 jobs:
-  checkout:
-    runs-on: self-hosted
-    steps:
-    - uses: actions/checkout@v4
   check_flurry_package:
     runs-on: self-hosted
     steps:
       - run: nix flake check -L --all-systems
   build_flurry_package:
     runs-on: self-hosted
-    needs: checkout
     steps:
       - run: nix build -L
   build_flurry_shell:
     runs-on: self-hosted
-    needs: checkout
     steps:
       - run: nix shell -L --command echo 'it works'