Update dependency dart to v3

renovate[bot] · web-flow · commit 87c25de9797b · 2023-08-25T05:43:46.000Z
diff --git a/pubspec.yaml b/pubspec.yaml
@@ -5,7 +5,7 @@ homepage: "https://github.com/MeowType/GraphDart"
 repository: "https://github.com/MeowType/GraphDart"
 issue_tracker: "https://github.com/MeowType/GraphDart/issues"
 environment:
-  sdk: ">=2.14.0 <3.0.0"
+  sdk: "<4.0.0"
 dependencies:
   some: ^2.0.0
 dev_dependencies:
