⬆️ Bump actions/upload-artifact from 5 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/cache.yml

@@ -33,13 +33,13 @@ jobs:
         run: |
           jb build lectures --path-output ./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: failure()
         with:
           name: execution-reports
           path: _build/html/reports
       - name: Upload "_build" folder (cache)
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: build-cache
           path: _build

.github/workflows/ci.yml

@@ -70,7 +70,7 @@ jobs:
         run: |
           jb build lectures --path-output ./ -n -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: failure()
         with:
           name: execution-reports

.github/workflows/execution-linux.yml

@@ -32,7 +32,7 @@ jobs:
         shell: bash -l {0}
         run: jb build lectures --path-output=./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: failure()
         with:
           name: execution-reports

.github/workflows/execution-osx.yml

@@ -32,7 +32,7 @@ jobs:
         shell: bash -l {0}
         run: jb build lectures --path-output=./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: failure()
         with:
           name: execution-reports

.github/workflows/execution-win.yml

@@ -37,7 +37,7 @@ jobs:
         shell: powershell
         run: jb build lectures --path-output=./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: failure()
         with:
           name: execution-reports

.github/workflows/publish.yml

@@ -73,7 +73,7 @@ jobs:
         run: |
           jb build lectures --path-output ./ --builder=custom --custom-builder=jupyter -n -W --keep-going
           zip -r download-notebooks.zip _build/jupyter
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: download-notebooks
           path: download-notebooks.zip