...

//According to this document, a 
 tag can only contain inline elements. That means putting a 
 tag inside it should be improper, since the div tag is a block element. Improper nesting might cause glitches like rendering extra tags, which can affect your javascript and css.

//If you want to get rid of this warning, you might want to customize the ReactTooltip component, or wait for the creator to fix this warning.
//If you're looking for where this is happening, in console you can use:
document.querySelectorAll(" p * div ")
//Here's another version that made finding the item more verbose for me 
document.querySelectorAll("p > div")