docs: remove the EOL warning banner

[luisrivas]

Contributing to Twilio

All third party contributors acknowledge that any contributions they provide will be made under the same open source license that the open source project is provided under.

• I acknowledge that all my contributions will be made under the project's license.

Pull Request Details

Description

Remove the end-of-life warning banner from the documentation.

Burndown

Before review

• Updated CHANGELOG.md if necessary
• Added unit tests if necessary
• Updated affected documentation
• Verified locally with npm test
• Manually sanity tested running locally
• Included screenshot as PR comment (if needed)
• Ready for review

Before merge

• Got one or more +1s
• Re-tested if necessary

[donaltoomey]

LGTM