[fuchsia] Clean-up after the FIDL string/vector types transition
[fuchsia] Clean-up after the FIDL string/vector types transition

This cleans up what was introduced in:
https://dart-review.googlesource.com/c/88122

Change-Id: If7596a3dd57af25d91fe880104e5aafd301c57f4
Reviewed-on: https://dart-review.googlesource.com/c/94922
Auto-Submit: Ian McKellar <2f9f6f5cf4302a9fc961983480ae9c9a0e48898a@google.com>
Reviewed-by: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>
Commit-Queue: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>

dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk