How do I change the owner of a system32 back to TrustedInstaller?

[Windows 10]

I had to change the owner of a system32 file because a troubleshooting guide required me to modify said file. To do that, I changed its owner to "everyone" (roughly as described in this post). Unfortunately, I cannot change it back to "TrustedInstaller", as I then get an error message that claims TrustedInstaller, cannot be entered (pic).

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