Bump dart-lang/setup-dart from 1.5.0 to 1.6.0 (#740)

Bumps [dart-lang/setup-dart](https://github.com/dart-lang/setup-dart) from 1.5.0 to 1.6.0.
- [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@d6a63da...b64355a)

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

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

.github/workflows/dart.yml

@@ -23,7 +23,7 @@ jobs:
  sdk: [dev]
  steps:
  - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744
- - uses: dart-lang/setup-dart@d6a63dab3335f427404425de0fbfed4686d93c4f
+ - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d
  with:
  sdk: ${{ matrix.sdk }}
  - id: install
@@ -50,7 +50,7 @@ jobs:
  sdk: [2.17.0, dev]
  steps:
  - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744
- - uses: dart-lang/setup-dart@d6a63dab3335f427404425de0fbfed4686d93c4f
+ - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d
  with:
  sdk: ${{ matrix.sdk }}
  - id: install