The ref is to the old Control Panel and select Programs and Features and then View installed updates.
from there you can remove the KB 1909 enablement package.
There has been a Dec 2019 Cumulative update that another user on another thread states fixes 1909 Search in File Explorer, but not in other search boxes. This would be fine but the update page for the KB update doesn't mention a fix for this update so it could be just a fluke.
https://support.microsoft.com/en-gb/help/4530684/windows-10-update-kb4530684
This problem need to be reported (and upvoted) in the Feedback Hub for MS to produce a fix. Writing about it here won't help fix it.