test: add testing for Switcher, SwitcherDivider and SwitcherItem

[francinelucca]

Closes #12859

Adds testing for Switcher, SwitcherDivider and SwitcherItem.
Also refactors test generator script to generate IBM Copyright header using current year.

Changelog

New

• packages/react/src/components/UIShell/tests/Switcher-test.js: add test file for Switcher
• packages/react/src/components/UIShell/tests/SwitcherDivider-test.js: add test file for SwitcherDivider
• packages/react/src/components/UIShell/tests/SwitcherItem-test.js: add. test file for SwitcherItem
• packages/react/tasks/build-test-rtl.js: generate IBM copyright header based on current year

Testing / Reviewing

Should test every prop in Switcher, SwitcherItem and SwitcherDivider and all tests should pass

[netlify]

✅ Deploy Preview for carbon-components-react ready!

Name	Link
🔨 Latest commit	e8c7459
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-components-react/deploys/64109f418635420008015afb
😎 Deploy Preview	https://deploy-preview-13342--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	e8c7459
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-elements/deploys/64109f41508e390008d2ee5b
😎 Deploy Preview	https://deploy-preview-13342--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.

[andreancardona]

just need to update copyright header :)