fix: remove non longer valid TwilioQuest badge from README

[tomczak-mateusz]

Purpose:

Currently there is a "TwilioQuest - Learn to contribute!" badge present in README:

When clicking the badge, the link is directing to non existing page:

When clicking the Return to the TwilioQuest Home Page link on the error page, the next view is informing that TwilioQuest program was sunseted at the end of March 2023.

This PR removes the badge from README as the program is non longer valid & it might be confusing for the new Twilio users to hit a non viable link.

Changes:

• removes TwilioQuest badge from README

Checklist

• [x] I acknowledge that all my contributions will be made under the project's license
• [ ] I have made a material change to the repo (functionality, testing, spelling, grammar)
• [x] I have read the Contribution Guidelines and my PR follows them
• [x] I have titled the PR appropriately
• [x] I have updated my branch with the main branch
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] I have added the necessary documentation about the functionality in the appropriate .md file
• [ ] I have added inline documentation to the code I modified