Bump go_router from 14.8.1 to 15.0.0 in /form_app

Bumps [go_router](https://github.com/flutter/packages/tree/main/packages) from 14.8.1 to 15.0.0.
- [Release notes](https://github.com/flutter/packages/releases)
- [Commits](https://github.com/flutter/packages/commits/go_router-v15.0.0/packages)

---
updated-dependencies:
- dependency-name: go_router
  dependency-version: 15.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

form_app/pubspec.yaml

@@ -18,7 +18,7 @@ dependencies:
     git:
       url: https://github.com/google/flutter-desktop-embedding.git
       path: plugins/window_size
-  go_router: ^14.0.0
+  go_router: ^15.0.0
 
 dev_dependencies:
   analysis_defaults: