refactor: remove intersection-observer polyfill

[Sultan-Q]

The intersection-observer polyfill is no longer needed as the Intersection Observer API has been supported by all major browsers since 2019 (Baseline). This change removes the polyfill dependency and its import.

Changes:

• Removed intersection-observer from packages/hooks/package.json dependencies.
• Removed import 'intersection-observer' from packages/hooks/src/useInViewport/index.ts

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