chore(deps): bump ffigen from 15.0.0 to 16.0.0 in /packages/mimir

Bumps [ffigen](https://github.com/dart-lang/native/tree/main/pkgs) from 15.0.0 to 16.0.0.
- [Release notes](https://github.com/dart-lang/native/releases)
- [Commits](https://github.com/dart-lang/native/commits/HEAD/pkgs)

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

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

packages/mimir/pubspec.yaml

@@ -18,6 +18,6 @@ dependencies:
 
 dev_dependencies:
   build_runner: ^2.3.2
-  ffigen: ^15.0.0
+  ffigen: ^16.0.0
   freezed: ^2.2.1
   test: ^1.22.0