Remove unnecessary deprecated declaration guards from ScreenCaptureKitCaptureSource since it no longer used deprecated APIs.
<rdar://problem/113036793>
Pull request: https://github.com/WebKit/WebKit/pull/16166
Committed 266402@main (01d1f208e1d0): <https://commits.webkit.org/266402@main> Reviewed commits have been landed. Closing PR #16166 and removing active labels.