Mitigate use of private macOS font API

Editor assessment

The subject states the mitigation precisely: use of a private macOS font API reduced. The fix type suits the risk-reduction change, and the absent scope is tolerable. No body is present, which is acceptable for a contained compatibility change whose target the subject names, though the breakage or rejection risk that motivated it would have been worth a line. The PR reference is well-formed. Imperative mood, no trailing period, compact length. A clear, self-sufficient compatibility message for a change of this size.