style: Apply nixfmt to trivial Nix files

ALl the ones except for build-image.nix are considered trivial. On the
latter, nixfmt makes some useful changes but by-and-large it is not
ready for that code yet.

build-image/go-deps.nix

@@ -1,6 +1,5 @@
 # This file was generated by https://github.com/kamilchm/go2nix v1.3.0
-[
-  {
+[{
   goPackagePath = "gonum.org/v1/gonum";
   fetch = {
     type = "git";
@@ -8,5 +7,4 @@
     rev = "ced62fe5104b907b6c16cb7e575c17b2e62ceddd";
     sha256 = "1b7q6haabnp53igpmvr6a2414yralhbrldixx4kbxxg1apy8jdjg";
   };
-  }
-]
+}]

default.nix

@@ -11,8 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-{ pkgs ? import <nixpkgs> {}
-, preLaunch ? "" }:
+{ pkgs ? import <nixpkgs> { }, preLaunch ? "" }:
 
 with pkgs;
 

shell.nix

@@ -20,8 +20,5 @@ let nixery = import ./default.nix { inherit pkgs; };
 in pkgs.stdenv.mkDerivation {
   name = "nixery-dev-shell";
 
-  buildInputs = with pkgs;[
-    jq
-    nixery.nixery-build-image
-  ];
+  buildInputs = with pkgs; [ jq nixery.nixery-build-image ];
 }