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/doc.yaml

@@ -47,7 +47,7 @@ jobs:
       - name: Build
         run: |
           rake doc:html
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: doc
           path: doc/build

.github/workflows/package.yaml

@@ -46,7 +46,7 @@ jobs:
       - name: Build archive
         run: |
           rake dist
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: source
           path: apache-arrow-flight-sql-postgresql-*.tar.gz
@@ -181,7 +181,7 @@ jobs:
             ./
           tar czf ${{ matrix.target }}.tar.gz ${DISTRIBUTION}
       - name: Upload artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: ${{ matrix.target }}
           path: |