можно так:
Can you do that:

procedure TMainForm.FormClose(Sender: TObject; var Action: TCloseAction);
var Dir:String;
begin
 Mainform.Visible:=false; 
 WebBrowser1.SelectedEngine:=IEOnly; // if Edge mode is enabled - turn off
 WebBrowser1.Navigate('about<b>/b>:blank'); 
 Sleep(1000); 
 WebBrowser1.Free; 
 Sleep(2000); 
 Dir:=Application.ExeName+'.WebView2'; 
 if DirectoryExists(Dir) then TDirectory.Delete(Dir, True); 
end;