Update auto_routing_improved.html

[jetzt-deins]

Added note, that namespaces must be adjusted

Description
Explain what you have changed, and why.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• [X ] User guide updated
• Conforms to style guide

[github-actions]

Thank you for your pull request. However, you have submitted your PR on a read-only split of codeigniter4/CodeIgniter4. This repository, unfortunately, does not accept PRs. Please submit your PR at https://github.com/codeigniter4/CodeIgniter4 repository.

Thank you.