On the about page for any place you can flag it for issues. In this case the page for Toronto already has two flags about this (and 2 previous forum threads):
https://www.inaturalist.org/flags/545806
https://www.inaturalist.org/flags/646004
Wonky County Borders - General
The boundaries of Toronto on the map are innacurate - Bug Reports
It looks like for this particular type of imported “place”, only staff can edit them. The recommendation is to use this user-created boundary instead: https://www.inaturalist.org/places/city-of-toronto-on-ca