fix: remove npm self-upgrade step from publish workflow

Node 22.22.2's bundled npm is missing promise-retry, causing
npm install -g npm@latest to fail. The upgrade is unnecessary
since actions/setup-node@v4 provides a working npm.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tianzhou

.github/workflows/publish.yml

@@ -121,11 +121,6 @@ jobs:
           node-version: "22"
           cache: "pnpm"
 
-      - name: Upgrade npm
-        run: |
-          npm install -g npm@latest
-          echo "npm version: $(npm --version)"
-
       - name: Install dependencies
         run: pnpm install --frozen-lockfile