fix: CSS animations not being removed from the stylesheet on web

[MatiPl01]

Summary

@m-bert noticed that animations aren't cleaned up from the Reanimated's CSS stylesheet when components are unmounted. As a result, we ended up having multiple instances of animations that were no longer used.

Example recording

Before

Screen.Recording.2025-07-29.at.15.24.55.mp4

After

Screen.Recording.2025-07-29.at.15.23.45.mp4

Test example

Code snippet

import { useState } from 'react';
import { Button } from 'react-native';
import Animated from 'react-native-reanimated';

export default function App() {
  const [show, setShow] = useState(false);

  return (
    <>
      <Button title="Show" onPress={() => setShow(!show)} />
      {show && (
        <Animated.View
          style={{
            backgroundColor: 'green',
            flex: 1,
            animationName: {
              from: { backgroundColor: 'red' },
              to: { backgroundColor: 'blue' },
            },
            animationDuration: '1s',
            animationTimingFunction: 'ease-in-out',
            animationDelay: '0s',
            animationIterationCount: 'infinite',
            animationDirection: 'alternate',
            animationFillMode: 'forwards',
            animationPlayState: 'running',
          }}
        />
      )}
    </>
  );
}