Revert "FIX: Composer height issue in Safari on iOS 15 (#14282)" (PR #14847)

This reverts commit 0dab1634b060077f18a741b0cf433571f3f523e9.

Fixed in iOS 15.1, we don’t need to carry this workaround anymore.

See also 229876 – iOS 15 Beta 8 VisualViewport.height does not account for address bar above virtual keyboard

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