docs(user-event): fix code example of clear API

[nimaebra]

Fix code example of clear API in user-events v13 docs.

The current code example does not work and causes confusion because React value prop without an onChange handler causes the field to be read-only. Also value attribute is null.

So I changed two things:

• value to defaultValue prop
• toHaveAttribute('value', '') to toHaveValue('')

The example code for clear in Utility APIs is also following this method.

[MatanBobi]

Hi @nimaebra, thanks for taking the time to open this one :)
I'm actually not sure the textarea element supports defaultValue based on the HTML spec

[nimaebra]

@MatanBobi, Thanks for your response 💯
The code example is written in react and according to the react docs, textarea supports defaultValue.
Additionally, as I mentioned in my quote, the clear code example of Utility APIs is also uses defaultValue for textarea.

[ph-fritsche]

Thanks for taking the time to fix this ❤️

[MatanBobi]

Thanks! :)
@all-contributors please add @nimaebra for docs :)

[MatanBobi]

@all-contributors please add @ph-fritsche for review :)

[allcontributors]

@MatanBobi

I've put up a pull request to add @ph-fritsche! 🎉