[Cocoa] Replace bool parameter to preparePlatformFont() with a 2-state enum
<rdar://problem/105439787>
Pull request: https://github.com/WebKit/WebKit/pull/10079
Committed 260250@main (999e6580a40d): <https://commits.webkit.org/260250@main> Reviewed commits have been landed. Closing PR #10079 and removing active labels.