Bump actions/download-artifact from 4 to 6 (#79)

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/push-master-pico.yml

@@ -134,7 +134,7 @@ jobs:
         run: echo "preRelease=true" >> $GITHUB_ENV
 
       - name: Download artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: artifacts
           pattern: release-artifact-*

.github/workflows/push-master.yml

@@ -77,7 +77,7 @@ jobs:
         if: contains(env.VERSION, 'alpha') || contains(env.VERSION, 'beta')
         run: echo "preRelease=true" >> $GITHUB_ENV
 
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: firmware-release