fix(code-snippet): scrollbar not clickable on muliline

[alisonjoseph]

closes #9946

Scrollbar wasn't clickable when there was an overflow on the multiline code snippet because the overflow-indicator-right div was being rendered to sit directly on top of it. This removes that div and adds the overflow gradient to the pre:after element instead.

Changelog

New

• add class for multiline when hasRightOverflow is true
• update styles for overflow gradient to show up on after element of pre to not interfere with scrollbar

Changed

• Only render overflow-indicator-right div for single line code snippet

Testing / Reviewing

Make sure you can scroll with the mouse all directions in multiline codesnippet and that the gradient shows up correctly. Check that single line didn't change at all.

Test with scrollbars on and off in your system settings.

[netlify]

✅ Deploy Preview for carbon-components-react ready!

Name	Link
🔨 Latest commit	4d099d3
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-components-react/deploys/636e9ea86fc042000aa07380
😎 Deploy Preview	https://deploy-preview-12605--carbon-components-react.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[netlify]

✅ Deploy Preview for carbon-elements ready!

Name	Link
🔨 Latest commit	4d099d3
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-elements/deploys/636e9ea84b113a000896bb28
😎 Deploy Preview	https://deploy-preview-12605--carbon-elements.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[tay1orjones]

Awesome! 🎉