chore(example/deps): update dependency dart to v3.9.4

[renovate]

This PR contains the following updates:

Package	Update	Change
dart (source)	patch	>=3.9.2 <4.0.0 → 3.9.4

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Release Notes

dart-lang/sdk (dart)

v3.9.4

Compare Source

Released on: 2025-09-30

Pub

• dart pub get --example will now resolve example/ folders in the
  entire workspace, not only in the root package.
  This fixes dart-lang/pub#4674 that made flutter pub get
  crash if the examples had not been resolved before resolving the workspace.

v3.9.3

Compare Source

Released on: 2025-09-09

Tools

Development JavaScript compiler (DDC)

• Fixes a pattern that could lead to exponentially slow compile times when
  static calls are deeply nested within a closure.
  When present this led to builds timing out or
  taking several minutes rather than several seconds.

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Configuration

📅 Schedule: Branch creation - "after 6pm every weekday,every weekend" in timezone Australia/Sydney, Automerge - "after 6pm every weekday,every weekend" in timezone Australia/Sydney.

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• If you want to rebase/retry this PR, check this box

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: example/pubspec.lock

Command failed: flutter pub get --no-precompile
The current Dart SDK version is 3.11.0.

Because firestore_cache_example requires SDK version 3.9.4, version solving failed.
Failed to update packages.