Enable react/jsx-key for fragment shorthands

[koesie10]

This will change ESLint to give an error when you do something like this:

{x.map((y) => <>{y.name}</>)}

In this case, there's no key being passed to the top-level element in a map. We should always explicitly pass in a key to make the best use of React. This can be fixed by doing this:

{x.map((y) => <Fragment key={y.id}>{y.name}</Fragment>)}

We ran into this in #2995: https://github.com/github/vscode-codeql/pull/2995/files#r1363990725

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[charisk]

Nice, thanks!