React: Change StoryFnReactReturnType to JSX.Element

[chakAs3]

Closes #

TypeCheck issue whenever we have a decorator like this

(Story) => (
      <>
        <p>Component Decorator</p>
        <Story />
      </>
    )

Story should return a valid JSX Element to be parsed in the template

What I did

StoryFnReactReturnType was set to ReactElement which is a general term used to refer to the objects that describe React components or HTML tags created using React.createElement() or JSX syntax.

However JSX.Element is a TypeScript type used to define the type of elements returned by JSX expressions,

and that is what StoryFn is actually returning

How to test

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]