[DOCS] React integration typo

[thanh-nguyencong]

Describe what the update does

Fix a typo in the documentation.

Provide the suggested modification

Change a comment in https://animejs.com/documentation/getting-started/using-with-react from

// Every anime.js instances declared here are now scopped to <div ref={root}>

to

// Every anime.js instance declared here is now scoped to <div ref={root}>

What changed:

• singular instance
• is instead of are
• scoped with 1 p