Bump actions/download-artifact from 4 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...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>

.github/workflows/ql-for-ql-dataset_measure.yml

@@ -76,7 +76,7 @@ jobs:
     needs: measure
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: measurements
           path: stats

.github/workflows/ruby-build.yml

@@ -147,19 +147,19 @@ jobs:
     needs: [build, compile-queries]
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: ruby.dbscheme
           path: ruby/ruby
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: extractor-ubuntu-latest
           path: ruby/linux64
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: extractor-windows-latest
           path: ruby/win64
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: extractor-macos-latest
           path: ruby/osx64
@@ -178,7 +178,7 @@ jobs:
           path: ruby/codeql-ruby.zip
           retention-days: 1
           include-hidden-files: true
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: codeql-ruby-queries
           path: ruby/qlpacks
@@ -214,7 +214,7 @@ jobs:
         uses: ./.github/actions/fetch-codeql
 
       - name: Download Ruby bundle
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: codeql-ruby-bundle
           path: ${{ runner.temp }}

.github/workflows/ruby-dataset-measure.yml

@@ -63,7 +63,7 @@ jobs:
     needs: measure
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           path: stats
       - run: |