fix: remove npm self-upgrade step that breaks release pipeline

npm@latest started shipping a broken install (missing promise-retry)
causing the release job to fail before any actual work happens.
The runner already ships with a recent enough npm for OIDC publishing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: piotrski

.github/workflows/release.yml

@@ -26,9 +26,6 @@ jobs:
         with:
           node-version: '22'
 
-      - name: Update npm for OIDC trusted publishing
-        run: npm install -g npm@latest
-
       - name: Install dependencies
         run: bun install