Bump actions/upload-artifact from 4 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/linux-build.yml

@@ -55,7 +55,7 @@ jobs:
           python -m pytest tests -v
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: pyoptinterface-wheel-${{ runner.os }}-${{ runner.arch }}-${{ matrix.python-version }}
           path: dist/

.github/workflows/macos-build.yml

@@ -52,7 +52,7 @@ jobs:
           python -m pytest tests -k "highs or ipopt" -v
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: pyoptinterface-wheel-${{ runner.os }}-${{ runner.arch }}-${{ matrix.python-version }}
           path: dist/

.github/workflows/wheel.yml

@@ -43,7 +43,7 @@ jobs:
           output-dir: wheelhouse
           config-file: "{package}/pyproject.toml"
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         with:
           name: cibw-wheels-${{ runner.os }}-${{ runner.arch }}
           path: ./wheelhouse/*.whl

.github/workflows/windows-build.yml

@@ -52,7 +52,7 @@ jobs:
           python -m pytest tests -v
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: pyoptinterface-wheel-${{ runner.os }}-${{ runner.arch }}-${{ matrix.python-version }}
           path: dist/