Python starter template has signed py files

After installing an official Aspire.ProjectTemplates templates, and `aspire new` -> pick `React (Vite) & FastAPI starter`, the .py files have a signing block at the end:

<img width="1666" height="980" alt="Image" src="https://github.com/user-attachments/assets/cd6ecbf6-b496-4c39-9152-c6bc79506e0e" />

We don't want this sign block to exist in our templates.