Bump actions/download-artifact from 2 to 4.1.7 in /.github/workflows

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 2 to 4.1.7.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v2...v4.1.7)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
...

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

.github/workflows/main.yml

@@ -76,12 +76,12 @@ jobs:
         with:
           submodules: true
       - name: Download target language compilation results
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v4.1.7
         with:
           name: targets
           path: _test/compiled
       - name: Download base-ubuntu_18.04
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v4.1.7
         with:
           name: base-ubuntu_18.04
           path: /tmp # downloads /tmp/kaitai-compress-test-base-ubuntu_18.04.tar