Why did we run that nix-build in nix-shell?

docs.nix used to use <nixpkgs> so maybe that was why

.gitlab-ci.yml

@@ -8,7 +8,7 @@ default:
 docs:
   stage: "build"
   script:
-    - "nix-shell --run 'nix-build docs.nix'"
+    - "nix-build docs.nix'
     - "cp --recursive --no-preserve=mode result/docs/. docs/build/"
   artifacts:
     paths: