Gaia Topo, as well as several other sources in the app, is based on OpenStreetMap data. OpenStreetMap (OSM) is an open-source, public mapping project that makes snap-to-trail routing possible.
If you find something on a map that you want to remove (or change), you can update OpenStreetMap, and this will be reflected on Gaia Topo when we launch the next rebuild of the planet. To remove or change something on the map, follow the steps in this article: