[0.66] Add back RCTDynamicColor, but remove references

[Saadnajmi]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

EDIT: Due to integration issues, I'll need to add back the RCTDynamicColor class to 0.66 as downstream components reference it.

(Same as #1060 but ported to 0.66-stable)
In #1028 I removed RCTDynamicColor.h/.m . There was still an explicit reference to the class in our unit tests. I'm not sure why that wasn't caught.

Changelog

[macOS] [Fixed] - Removed reference to RCTDynamicColor in our unit tests.

Test Plan

CI should pass.

[pull-bot]

	Warnings
⚠️	❔ Base Branch - The base branch for this PR is something other than main. Are you sure you want to merge these changes into a stable release? If you are interested in backporting updates to an older release, the suggested approach is to land those changes on main first and then cherry-pick the commits into the branch for that release. The Releases Guide has more information.

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[ghost]

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