Bump actions/upload-artifact from 6 to 7

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

---
updated-dependencies:
- dependency-name: actions/upload-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.yml

@@ -41,7 +41,7 @@ jobs:
           echo "isotag=${VER}-${REL}" >> $GITHUB_ENV
 
       - name: Upload iso artifact
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: mbp-linuxmint-cinnamon-${{ steps.tag.outputs.tag }}.z01
           path: ${{ github.workspace }}/output/*
@@ -109,7 +109,7 @@ jobs:
           echo "isotag=${VER}-${REL}" >> $GITHUB_ENV
 
       - name: Upload iso artifact
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: mbp-linuxmint-mate-${{ steps.tag.outputs.tag }}.z01
           path: ${{ github.workspace }}/output/*
@@ -172,7 +172,7 @@ jobs:
           echo "isotag=${VER}-${REL}" >> $GITHUB_ENV
 
       - name: Upload iso artifact
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: mbp-linuxmint-xfce-${{ steps.tag.outputs.tag }}.z01
           path: ${{ github.workspace }}/output/*