from App-->delete deployment dir and then Please try incognito window if you remove the logo as Maarten Bongers suggested it should go empty might be an catching issue.
If not working please create a transparent image and give that as logo for workaround.
If its a project in maintainance check index.html or similer
it might be hard coded there in <head> element with <link rel=icon …...
You can select a logo or no logos from the navigation > the application icon.