[Docs] jsx-key: fix correct example

[developer-bandi]

In the 3rd item of the correct example, x.id is used as the key. However, since an number type array is entered in Array.from, x is a number, all keys have undefined. Additionally, searching the number property is generally considered an error in TypeScript.

Therefore, the key was modified to use x itself so that the key has a unique value and does not cause an error in TypeScript.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3fb79e1) 97.65% compared to head (48318fa) 97.65%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3656   +/-   ##
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  Coverage   97.65%   97.65%           
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  Files         132      132           
  Lines        9375     9375           
  Branches     3432     3432           
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  Hits         9155     9155           
  Misses        220      220           

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