Bump actions/download-artifact from 5 to 6

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] <[email protected]>

Author: dependabot[bot]

.github/workflows/main.yml

@@ -266,39 +266,39 @@ jobs:
       - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: ubuntu-latest-3.9
           path: /tmp/u39
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: ubuntu-latest-3.10
           path: /tmp/u310
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: ubuntu-latest-3.11
           path: /tmp/u311
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: ubuntu-latest-3.12
           path: /tmp/u312
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: ubuntu-latest-3.13
           path: /tmp/u313
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: macos-latest-3.9
           path: /tmp/m39
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: macos-latest-3.13
           path: /tmp/m313
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: windows-latest-3.9
           path: /tmp/w39
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: windows-latest-3.13
           path: /tmp/w313