Bump actions/download-artifact from 4 to 6 (#125)

Author: dependabot[bot]

.github/workflows/flare.yml

@@ -205,7 +205,7 @@ jobs:
     runs-on: macos-15
     steps:
       - name: Download artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: test_output
       - run: xcrun xcresulttool merge test_output/**/*.xcresult --output-path test_output/final/final.xcresult

.github/workflows/flare_ui.yml

@@ -236,7 +236,7 @@ jobs:
     runs-on: macos-15
     steps:
       - name: Download artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: test_output
       - run: xcrun xcresulttool merge test_output/**/*.xcresult --output-path test_output/final/final.xcresult