ci: align Node version with .node-version to fix pkg-pr-new fetch crash

Node 20.10.0 ships undici 5.27.x, which has a race where fetch's
ReadableStream controller closes before enqueue, causing pkg-pr-new
publish to crash with ERR_INVALID_STATE. Reading from .node-version
matches ci-fork.yml and picks up a Node with the undici fix.

Author: ryanbas21

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/setup-node@v4
         id: cache
         with:
-          node-version: '20.10.0'
+          node-version-file: '.node-version'
           cache: 'pnpm'
 
       - run: pnpm install --frozen-lockfile