[Bug]: accessibly comment reply text box on iOS

### What happened?

The comment reply box’s `textarea` is not picked up by a11y tooling on iOS, as per @tkgnm’s [iOS review](https://github.com/guardian/ios-live/pull/7779#pullrequestreview-2009297495)

### Where is this happening?

https://www.theguardian.com/lifeandstyle/2024/apr/19/you-be-the-judge-should-my-sister-help-me-challenge-our-brothers-sexist-views#comments

### What is the impact?

This may prevent users relying on assitive technology from participating in our discussions