build(deps): bump actions/upload-artifact from 3 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v3...v4)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/ex-rtd.yml

@@ -104,7 +104,7 @@ jobs:
         run: ls -R .doc/_notebooks/
 
       - name: Upload completed jupyter notebooks as an artifact for ReadtheDocs
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: rtd-files-for-${{ github.sha }}
           path: |

.github/workflows/ex-workflow.yml

@@ -74,7 +74,7 @@ jobs:
         shell: python
 
       - name: Upload build artifacts for current release
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: zip_files
           path: |
@@ -190,7 +190,7 @@ jobs:
 
       - name: Upload build artifacts for current release
         if: matrix.python == '3.9'
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: current
           path: |