chore: upgrade eslint-scope to v9

[Pixel998]

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What is the purpose of this pull request?

This PR upgrades eslint-scope to the latest version and removes the separate @types/eslint-scope dependency now that eslint-scope ships its own TypeScript declarations.

What changes did you make? (Give an overview)

• Upgraded eslint-scope from ^8.4.0 to ^9.1.2
• Removed @types/eslint-scope from devDependencies
• Removed a stale sourceType as never cast.

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