chore(deps): bump ffigen

Bumps the ffigen group in /packages/auth/amplify_auth_cognito_dart with 1 update: [ffigen](https://github.com/dart-lang/native/tree/main/pkgs).


Updates `ffigen` from 9.0.1 to 20.1.1
- [Release notes](https://github.com/dart-lang/native/releases)
- [Commits](https://github.com/dart-lang/native/commits/ffigen-v20.1.1/pkgs)

---
updated-dependencies:
- dependency-name: ffigen
  dependency-version: 20.1.1
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: ffigen
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

packages/auth/amplify_auth_cognito_dart/pubspec.yaml

@@ -45,7 +45,7 @@ dev_dependencies:
   build_verify: ^3.0.0
   build_web_compilers: ^4.1.4
   built_value_generator: ^8.10.1
-  ffigen: ^9.0.0
+  ffigen: ">=9.0.0 <21.0.0"
   json_serializable: ^6.11.0
   mockito: ^5.0.0
   smithy_codegen: