build(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](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/build-nodes.yml

@@ -49,7 +49,7 @@ jobs:
           cargo strip
 
       - name: upload substrate binary
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: nightly-substrate-binary
           path: target/release/substrate-node
@@ -62,7 +62,7 @@ jobs:
           tar -zcvf target/release/polkadot.tar.gz target/release/polkadot
 
       - name: upload polkadot binary
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: nightly-polkadot-binary
           path: |