Gnome-shell extension disabling hotcorners.
This extension is not needed anymore. Since 3.34, you can disable the hot corner with gsettings or using gnome-tweak-tool.
The gsettings command is:
gsettings set org.gnome.desktop.interface enable-hot-corners false
On some old Ubuntu versions (and probably derived), it's:
gsettings set org.gnome.shell enable-hot-corners false