Bump dart-lang/setup-dart from 1.8.0 to 1.8.1 (#29)

Bumps [dart-lang/setup-dart](https://github.com/dart-lang/setup-dart) from 1.8.0 to 1.8.1.
- [Release notes](https://github.com/dart-lang/setup-dart/releases)
- [Changelog](https://github.com/dart-lang/setup-dart/blob/main/CHANGELOG.md)
- [Commits](dart-lang/setup-dart@7654d45...6afc89d)

---
updated-dependencies:
- dependency-name: dart-lang/setup-dart
  dependency-version: 1.8.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

.github/workflows/dart.yml

@@ -23,7 +23,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
         with:
           submodules: true
-      - uses: dart-lang/setup-dart@7654d458321ee25acccccfdb86cd48bd95768ff1
+      - uses: dart-lang/setup-dart@6afc89df92d6eb3834022f73cd65adc8cdfcb92d
         with:
           sdk: ${{ matrix.sdk }}
       - name: Install dependencies