Bump google_fonts from 5.1.0 to 6.0.0 in /experimental/linting_tool (#2019)

Bumps [google_fonts](https://github.com/material-foundation/flutter-packages/tree/main/packages) from 5.1.0 to 6.0.0.
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experimental/linting_tool/pubspec.yaml

@@ -16,7 +16,7 @@ dependencies:
   equatable: ^2.0.3
   file_selector: ^1.0.0
   flutter_markdown: ^0.6.2
-  google_fonts: ^5.0.0
+  google_fonts: ^6.0.0
   hive: ^2.0.4
   hive_flutter: ^1.1.0
   http: ^1.0.0