Bump fluent_ui from 3.12.0 to 4.0.0 in /simplistic_calculator (#1439)

Bumps [fluent_ui](https://github.com/bdlukaa/fluent_ui) from 3.12.0 to 4.0.0.
- [Release notes](https://github.com/bdlukaa/fluent_ui/releases)
- [Changelog](https://github.com/bdlukaa/fluent_ui/blob/master/CHANGELOG.md)
- [Commits](https://github.com/bdlukaa/fluent_ui/compare/v3.12.0...v4.0.0)

---
updated-dependencies:
- dependency-name: fluent_ui
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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simplistic_calculator/pubspec.yaml

@@ -9,7 +9,7 @@ environment:
 dependencies:
   auto_size_text: ^3.0.0
   cupertino_icons: ^1.0.2
-  fluent_ui: ^3.11.1
+  fluent_ui: ^4.0.0
   fluentui_system_icons: ^1.1.168
   flutter:
     sdk: flutter