Rename WTF_OS_MAC_OS_X to WTF_OS_MACOS
Pull request: https://github.com/WebKit/WebKit/pull/8105
Committed 258363@main (f54ab6989687): <https://commits.webkit.org/258363@main> Reviewed commits have been landed. Closing PR #8105 and removing active labels.
<rdar://problem/103779773>