ci: 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](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>

.github/workflows/release.yml

@@ -67,14 +67,14 @@ jobs:
           ./scripts/genappimage.sh ${{ needs.setup.outputs.appimage_tag }}
       - name: tar.gz
         run: cpack --config build/CPackConfig.cmake -G TGZ
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: nvim-appimage-${{ matrix.arch }}
           path: |
             build/bin/nvim-linux-${{ matrix.arch }}.appimage
             build/bin/nvim-linux-${{ matrix.arch }}.appimage.zsync
           retention-days: 1
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: nvim-linux-${{ matrix.arch }}
           path: |
@@ -124,7 +124,7 @@ jobs:
       - name: Package
         run: cpack --config build/CPackConfig.cmake
 
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: nvim-macos-${{ matrix.arch }}
           path: build/nvim-macos-${{ matrix.arch }}.tar.gz
@@ -164,7 +164,7 @@ jobs:
           cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=${{ needs.setup.outputs.build_type }}
           cmake --build build --target package
       - name: Upload artifact
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: nvim-win-${{ matrix.arch }}
           path: |