Bug - [deps] - React imports in examples/demos still required after JSX transform changes

[mfrances17]

Describe the problem
Follow-up to 11582, which addressed the new JSX transform changes. Some MD files were changed to consolidate all required React imports at the top of the MD file, which was required to build the docs, but were removed from the examples themselves. This could lead to a bad user experience because if the examples were copied/pasted, they might not work as expected without the required imports.

How do you reproduce the problem?
Affected subset of demos and/or examples without the imports will produce reference errors and won't load correctly if copied/pasted into another environment.

Expected behavior
Demos and examples can be copied/pasted as expected.

[mfrances17]

This is no longer an issue after fixes related to #11658.