Move off of UIKit SPI: `_UISheetDetent`
<rdar://problem/115331913>
Pull request: https://github.com/WebKit/WebKit/pull/17761
*** Bug 261456 has been marked as a duplicate of this bug. ***
Committed 267978@main (6f6557cd266c): <https://commits.webkit.org/267978@main> Reviewed commits have been landed. Closing PR #17761 and removing active labels.