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/ci.yml

@@ -115,7 +115,7 @@ jobs:
           flags: unit-tests
       - name: Upload test results
         if: ${{ always() }} # Always run this step, even if tests fail
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: Unittest report ${{ matrix.os }}-${{ matrix.pixi-environment }}
           path: ${{ env.COVERAGE_REPORT }}
@@ -157,7 +157,7 @@ jobs:
           flags: integration-tests
       - name: Upload test results
         if: ${{ always() }} # Always run this step, even if tests fail
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: Integration test report ${{ matrix.os }}-${{ matrix.pixi-environment }}
           path: ${{ env.COVERAGE_REPORT }}
@@ -169,7 +169,7 @@ jobs:
       - typechecking
     steps:
       - name: Merge Artifacts
-        uses: actions/upload-artifact/merge@v5
+        uses: actions/upload-artifact/merge@v6
         with:
           name: Testing reports
           pattern: "* report *"
@@ -196,7 +196,7 @@ jobs:
           pixi run typing --non-interactive --html-report mypy-report
       - name: Upload test results
         if: ${{ always() }} # Upload even on mypy error
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: Mypy report
           path: mypy-report

.github/workflows/pypi-release.yml

@@ -42,7 +42,7 @@ jobs:
           else
             echo "✅ Looks good"
           fi
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: releases
           path: dist