chore(deps): 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] <[email protected]>

Author: dependabot[bot]

.github/workflows/pull_request.yml

@@ -41,7 +41,7 @@ jobs:
         run: uv run inv docs
 
       - name: Upload libdoc
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: SchemathesisLibrary-${{ matrix.python-version }}.html
           path: docs/SchemathesisLibrary.html
@@ -50,14 +50,14 @@ jobs:
         run: uv run inv atest
 
       - name: Upload runner test results
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: atest-result-runner-${{ matrix.python-version }}
           path: atest/output_runner/
 
       - name: Upload library test results
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: atest-result-library-${{ matrix.python-version }}

.github/workflows/release.yml

@@ -33,14 +33,14 @@ jobs:
         run: |
           uv run inv atest
       - name: Upload runner test results
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: atest-result-runner-python-3.13
           path: atest/output_runner/
       - name: Upload library test results
         if: always()
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: atest-result-library-python-3.13
           path: atest/output_library/