React 19 docs - do not advise to add a key in getLineProps + getTokenProps

[slorber]

Starting React 18.3, this kind of code:

const lineTokens = line.map((token, key) => (
  <span key={key} {...getTokenProps({token, key})} />
));

leads to the following warning:

Warning: A props object containing a "key" prop is being spread into JSX:
  let props = {key: someKey, className: ..., children: ..., style: ...};
  <span {...props} />
React keys must be passed directly to JSX without using spread:
  let props = {className: ..., children: ..., style: ...};
  <span key={someKey} {...props} />
    at CodeBlockLine (webpack-internal:///../packages/docusaurus-theme-classic/lib/theme/CodeBlock/Line/index.js:10:26)

I think the doc is a bit confusing (it led us to historically write the code above, although it's not what you show in the examples) while the key should rather be kept outside the PRR API calls, not spreading it.

This should be enough:

const lineTokens = line.map((token, key) => (
  <span key={key} {...getTokenProps({token})} />
));

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Docusaurus fixing React v18.3 warnings: facebook/docusaurus#10079

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[carbonrobot]

Appreciate the contribution! Will merge shortly