Bump actions/download-artifact from 4 to 6 (#30)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@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] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -170,7 +170,7 @@ jobs:
               winpthreads-git-12.0.0.r688.g6b2176247-1
     steps:
       - name: Download MSYS2
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: msys2-${{ matrix.sys }}
 
@@ -374,7 +374,7 @@ jobs:
 
       - name: Download vcpkg
         if: matrix.ruby-version == 'mswin'
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: vcpkg-${{ matrix.triplet }}
 
@@ -408,7 +408,7 @@ jobs:
           '@ | Tee-Object -FilePath "${env:GITHUB_ENV}" -Append -Encoding UTF8
 
       - name: Download MSYS2
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: msys2-${{ matrix.sys }}${{ matrix.variant }}
 
@@ -466,7 +466,7 @@ jobs:
           GH_TOKEN: ${{ github.token }}
 
       - name: Download Artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: b
           pattern: '*-packages-txt'
@@ -497,7 +497,7 @@ jobs:
           sparse-checkout-cone-mode: false
 
       - name: Download Artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           merge-multiple: true