Refactor some docs

[remcohaszing]

estree-util-build-jsx was updated to version 3, which uses spread syntax. However, some documentation was still using Object.assign in output examples.

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Name	Status	Preview	Comments	Updated (UTC)
mdx	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 19, 2023 10:11am

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Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (44ca1ff) 100.00% compared to head (6f84da2) 100.00%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2375 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 23 23 Lines 2499 2499 Branches 4 4 ========================================= Hits 2499 2499 ```

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[wooorm]

I’m still about to go through all the docs, and check all input/output examples.

Do you think you have all? I can merge but I’ll go through everything anyway!

[remcohaszing]

Ah ok, I thought maybe you missed this. These were all occurrences of Object.assign.