fix(react): update the query builder snippets

[Hristo313]

Closes #240

Checklist:

• check topic's TOC/menu and paragraph headings
• Include TOC topic labels in the topic content when it has a valuable update, is new, or is considered preview / beta
• link to other topics using ../relative/path.md
• at the References section at the end of the topic add links to topics, samples, etc
• reference API documentation instead of adding a section with API

• use valid component names - [Data] Grid, IgxSelectComponent, <igx-combo>
• use spell checker tool (VS Code, Grammarly, Microsoft Editor)
• add inline code blocks for the names of classes / tags / properties
• add language descriptor for the code blocks
• check if links function by running the check-api/mdx npm commands
• check if sample is working and fully visible in the topic
• check if sample is working and fully visible in the StackBlitz
• check if code blocks match the code in StackBlitz demo
• add or update meaningful llms.description metadata and run npm run check:llms-metadata

• follow SEO guidelines to fill topic's metadata (SEO guidelines)

• do not resolve requested changes (leave that to the reviewer)

[Copilot]

Pull request overview

Updates the React Query Builder documentation snippets to use functional components and React hooks instead of deprecated class component patterns, aligning the docs with current React best practices (per #240).

Changes:

• Replaced class lifecycle patterns (constructor, componentDidMount, componentWillUnmount) with useRef/useState/useEffect in React snippets.
• Updated template-related React snippets to remove this.* usage in favor of function-scope callbacks.
• Adjusted code block language identifiers to better match the shown JSX/TSX snippets.

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