fix: run pnpm install with --no-frozen-lockfile

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: blockPackageJson unable to update lockfile in transition mode CI #2010
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

🎁

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.80%. Comparing base (985e661) to head (189cb56).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2011   +/-   ##
=======================================
  Coverage   99.80%   99.80%           
=======================================
  Files         113      113           
  Lines        4573     4573           
  Branches      285      285           
=======================================
  Hits         4564     4564           
  Misses          9        9           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

🎉 This is included in version v2.9.4 🎉

The release is available on:

• GitHub releases
• npm package (@latest dist-tag)

Cheers! 📦🚀