chore(deps): bump ffigen (#222)

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


Updates `ffigen` from 14.0.1 to 15.0.0
- [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
  dependency-group: shorebird_code_push-deps
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

shorebird_code_push/pubspec.yaml

@@ -12,7 +12,7 @@ dependencies:
   meta: ^1.9.1
 
 dev_dependencies:
-  ffigen: ">=8.0.2 <15.0.0"
+  ffigen: ">=8.0.2 <16.0.0"
   mocktail: ">=0.3.0 <2.0.0"
   test: ^1.19.2
   very_good_analysis: ">=5.0.0 <7.0.0"