Fixed typings for React 19

[Venryx]

Description

Replaced references to JSX.Element with React.JSX.Element, as mentioned in the React 19 upgrade guide here: https://react.dev/blog/2024/04/25/react-19-upgrade-guide#the-jsx-namespace-in-typescript

Motivation and Context

React 19 no longer provides the JSX.Element type; instead, it is present at React.JSX.Element. (as seen in link above)

Checklist

[X] I have not included any built dist files (us maintainers do that prior to a new release)
[n/a] I have added tests covering my changes
[n/a] All new and existing tests pass
[ ] My changes required the documentation to be updated
  [ ] I have updated the documentation accordingly
  [ ] I have updated the TypeScript 1.8 type definitions accordingly
  [ ] I have updated the TypeScript 2.0+ type definitions accordingly