doc: update Nix code snippets format

Command: `mdcr --config doc/tests/mdcr-config.toml doc/`

doc/languages-frameworks/dart.section.md

@@ -30,7 +30,11 @@ The `dart` commands run can be overridden through `pubGetScript` and `dartCompil
 Dart supports multiple [outputs types](https://dart.dev/tools/dart-compile#types-of-output), you can choose between them using `dartOutputType` (defaults to `exe`). If you want to override the binaries path or the source path they come from, you can use `dartEntryPoints`. Outputs that require a runtime will automatically be wrapped with the relevant runtime (`dartaotruntime` for `aot-snapshot`, `dart run` for `jit-snapshot` and `kernel`, `node` for `js`), this can be overridden through `dartRuntimeCommand`.
 
 ```nix
-{ lib, buildDartApplication, fetchFromGitHub }:
+{
+  lib,
+  buildDartApplication,
+  fetchFromGitHub,
+}:
 
 buildDartApplication rec {
   pname = "dart-sass";
@@ -101,7 +105,7 @@ See the [Dart documentation](#ssec-dart-applications) for more details on requir
 `flutter` in Nixpkgs always points to `flutterPackages.stable`, which is the latest packaged version. To avoid unforeseen breakage during upgrade, packages in Nixpkgs should use a specific flutter version, such as `flutter319` and `flutter322`, instead of using `flutter` directly.
 
 ```nix
-{  flutter322, fetchFromGitHub }:
+{ flutter322, fetchFromGitHub }:
 
 flutter322.buildFlutterApplication {
   pname = "firmware-updater";