Bump actions/download-artifact from 4 to 5

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 5.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v4...v5)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v5
         with:
           name: pdf
       - uses: actions/setup-node@v4
@@ -47,7 +47,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v5
         with:
           name: pdf
       - run: |
@@ -79,7 +79,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.ref == 'refs/heads/master'
     steps:
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v5
       - run: mv */index.html ./
       - run: mv */*/*.* ./
       - uses: peaceiris/actions-gh-pages@v4.0.0