chore(deps): bump ffigen

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


Updates `ffigen` from 9.0.1 to 21.0.0
- [Release notes](https://github.com/dart-lang/native/releases)
- [Commits](https://github.com/dart-lang/native/commits/ffigen-v21.0.0/pkgs)

---
updated-dependencies:
- dependency-name: ffigen
  dependency-version: 21.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: ffigen
...

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

Author: dependabot[bot]

packages/secure_storage/amplify_secure_storage_dart/pubspec.yaml

@@ -40,7 +40,7 @@ dev_dependencies:
   build_runner: ^2.4.15
   build_web_compilers: ^4.1.4
   built_value_generator: ^8.10.1
-  ffigen: ^9.0.0
+  ffigen: ">=9.0.0 <22.0.0"
   test: ^1.22.1
   worker_bee_builder: ">=0.3.12 <0.4.0"