fix(scripts): send check-prerequisites.ps1 errors to stderr#3123

mnriem merged 2 commits into

github:maingithub/spec-kit:mainfrom

Quratulain-bilal:fix/check-prereqs-errors-to-stderrQuratulain-bilal/spec-kit:fix/check-prereqs-errors-to-stderrCopy head branch name to clipboard