📝 Update code examples to Python 3.9

[YuriiMotov]

No description provided.

[github-actions]

📝 Docs preview

Last commit ae9b85c at: https://ddfb1ff6.asyncer.pages.dev

Modified Pages

• https://ddfb1ff6.asyncer.pages.dev/management-tasks/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/asyncify/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/first-steps/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/runnify/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/soonify-return/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/soonify/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/syncify-no-raise/ - (before)
• https://ddfb1ff6.asyncer.pages.dev/tutorial/syncify/ - (before)

[github-actions]

This pull request has a merge conflict that needs to be resolved.