remove all target which was never all anyway

docs/contributing.md

@@ -21,8 +21,6 @@ gets updated. I intend to upstream to nixpkgs as much of those as makes sense.
 Run all tests:
 
 ```bash
-$ nix build .#checks.${system}.all
-# or
 $ nix flake check
 # or
 $ nix run github:Mic92/nix-fast-build -- --skip-cached --flake ".#checks.$(nix eval --raw --impure --expr builtins.currentSystem)"

flake.nix

@@ -99,10 +99,6 @@
 
             shblib = pkgs.callPackage ./lib {};
           in (rec {
-            all = mergeTests [
-              modules
-            ];
-
             modules = shblib.check {
               inherit pkgs;
               tests =