Bump actions/download-artifact from 6 to 7

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 6 to 7.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v6...v7)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci-irctest.yml

@@ -54,7 +54,7 @@ jobs:
     - build
     steps:
       - name: Download build artifacts
-        uses: actions/download-artifact@v6
+        uses: actions/download-artifact@v7
         with:
           name: installed-inspircd-for-irctest
           path: "~"