Bump actions/download-artifact from 5 to 6 (#14)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/build.yml

@@ -84,7 +84,7 @@ jobs:
 
     steps:
       - name: Download Artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: dart-${{ inputs.ref }}-${{ matrix.host-arch }}
 

.github/workflows/release.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
       - name: Download Artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           pattern: dartsdk-android-*-${{ github.ref_name }}
           merge-multiple: true
@@ -49,7 +49,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Download Artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           pattern: dartsdk-android-*-${{ github.ref_name }}
           merge-multiple: true