fix: adjust examples

[sarahdayan]

@baileypeter found some styling issues in the embedded examples, mostly caused by outdated markup. While I was at it, I cleaned up the code snippets and CodeSandbox examples that had outdated markup as well.

[codesandbox-ci]

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Sandbox	Source
@algolia/autocomplete-example-github-repositories-custom-plugin	Configuration
@algolia/autocomplete-example-playground	Configuration
@algolia/autocomplete-example-query-suggestion-with-categories	Configuration
@algolia/autocomplete-example-query-suggestions-with-hits	Configuration
@algolia/autocomplete-example-query-suggestions-with-inline-categories	Configuration
@algolia/autocomplete-example-query-suggestions-with-recent-searches	Configuration
@algolia/autocomplete-example-query-suggestions	Configuration
@algolia/autocomplete-example-react-renderer	Configuration
@algolia/autocomplete-example-recently-viewed-items	Configuration
@algolia/autocomplete-example-starter	Configuration