Bump actions/setup-node from 4 to 6

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 4 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@v4...v6)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

action.yml

@@ -95,7 +95,7 @@ outputs:
 runs:
   using: 'composite'
   steps:
-    - uses: actions/setup-node@v4
+    - uses: actions/setup-node@v6
       with:
         node-version: '22'
     - name: Cache Copilot CLI