Update the README.md

[Jalithc]

**Update the README.md ** There Staging Site URL on the README.md is doesn't work. It need to update with new URL. There https://staging.python.org/ is doesn't working.

To Reproduce Steps to reproduce the behavior:

1. Go to 'pythondotorg'
2. Click on 'README.md'
3. Scroll down to 'Staging Site: https://staging.python.org/'
4. See error

Expected behavior README.md need to update this URL.

Desktop (please complete the following information):

• OS: [Windows]
• Browser [chrome]