build(deps): bump dart-lang/setup-dart from 1.5.1 to 1.6.0

Bumps [dart-lang/setup-dart](https://github.com/dart-lang/setup-dart) from 1.5.1 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@8a4b97e...b64355a)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/at_client_sdk.yaml

@@ -25,7 +25,7 @@ jobs:
       # Note: This workflow uses the latest stable version of the Dart SDK.
       # You can specify other versions if desired, see documentation here:
       # https://github.com/dart-lang/setup-dart/blob/main/README.md
-      - uses: dart-lang/setup-dart@8a4b97ea2017cc079571daec46542f76189836b1 # v1.5.1
+      - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d # v1.6.0
         with:
           sdk: stable
 
@@ -98,7 +98,7 @@ jobs:
       # Note: This workflow uses the latest stable version of the Dart SDK.
       # You can specify other versions if desired, see documentation here:
       # https://github.com/dart-lang/setup-dart/blob/main/README.md
-      - uses: dart-lang/setup-dart@8a4b97ea2017cc079571daec46542f76189836b1 # v1.5.1
+      - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d # v1.6.0
         with:
           sdk: stable
 
@@ -172,7 +172,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
-      - uses: dart-lang/setup-dart@8a4b97ea2017cc079571daec46542f76189836b1 # v1.5.1
+      - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d # v1.6.0
         with:
           sdk: stable
 
@@ -223,7 +223,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
-      - uses: dart-lang/setup-dart@8a4b97ea2017cc079571daec46542f76189836b1 # v1.5.1
+      - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d # v1.6.0
         with:
           sdk: stable