Done!
https://www.inaturalist.org/places/deer-lakes-park
Because of the new restrictions on places, it wasn’t as simple as changing the polygon. I created the KML file on Google My Maps because I could trace the Google boundary, but then iNat didn’t recognize the file. Using the tips here, I downloaded the existing KML file, opened both KML files in TextEdit, and pasted the coordinates (without altitude) from my new KML into the old one. Then it uploaded fine.