Document HostFunction dtor threading requirement

[motiz88]

Summary: Changelog: [Internal]

Updates the doc comment on Function::createFromHostFunction to mention that (a copy of) the provided std::function may be destroyed on an arbitrary thread, much like HostObject (where this is already documented).

Differential Revision: D56628194

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	19,460,108	+21
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	22,833,629	-6
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: 67392cef3c8e036adfd9f77808419221d70f8f18 Branch: main

[javache]

Merged as https://github.com/facebook/react-native/commit/694e8e7dce0d57a597a8b5443ff88c9a2755ebb1