Bump actions/upload-artifact from 5 to 6 (#8083)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](https://github.com/actions/upload-artifact/compare/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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/daily-test-improver.lock.yml

@@ -797,7 +797,7 @@ jobs:
               .write();
       - name: Upload agentic run info
         if: always()
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: aw_info.json
           path: /tmp/aw_info.json
@@ -906,7 +906,7 @@ jobs:
           echo "" >> $GITHUB_STEP_SUMMARY
       - name: Upload agentic output file
         if: always()
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: safe_output.jsonl
           path: ${{ env.GITHUB_AW_SAFE_OUTPUTS }}
@@ -1854,7 +1854,7 @@ jobs:
             await main();
       - name: Upload sanitized agent output
         if: always() && env.GITHUB_AW_AGENT_OUTPUT
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: agent_output.json
           path: ${{ env.GITHUB_AW_AGENT_OUTPUT }}
@@ -2391,7 +2391,7 @@ jobs:
             main();
       - name: Upload agent logs
         if: always()
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: daily-test-coverage-improver.log
           path: /tmp/daily-test-coverage-improver.log
@@ -2485,7 +2485,7 @@ jobs:
           fi
       - name: Upload git patch
         if: always()
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: aw.patch
           path: /tmp/aw.patch