Remove outdated quick-start README that documented deleted example app

The docs/quick-start-readme.md file documented the spec/quick-start example
app which was removed in the previous commit. The new docs/quick-start/README.md
from master provides a much better hands-on tutorial for users.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: justin808