chore: remove intersection-observer for old Safari support

[shuuji3]

This PR removes the old intersection-observer polyfill library introduced by #3191, similar to the previous PR #22693. The library repository had been archived already: GoogleChromeLabs/intersection-observer: A polyfill for IntersectionObserver - https://github.com/GoogleChromeLabs/intersection-observer.

This feature is natively supported by Safari since March 2019: "intersection-observer" | Can I use... Support tables for HTML5, CSS3, etc.

There's still intersection-observer in yarn.lock. This is because the old version of emoji-mart depends on it but the latest version doesn't have the dependency so it will be removed once we update the version of emoji-mart.

> yarn list
...
├─ emoji-mart@3.0.1-j
│  ├─ @babel/runtime@^7.0.0
│  ├─ intersection-observer@^0.12.0
│  └─ prop-types@^15.6.0
...
├─ intersection-observer@0.12.2 <- removing this
...

I'll open the PR once checked if this removal does not affect codes using IntersectionObserver.

[shuuji3]

Synced to the latest commit and it solved the lint error, which was caused by the old import of object-fit polyfill.