Remove shopping cart site header gradient

Hello, 

I'd like to remove the gradient from the site header on the Shopping Cart page but have had no luck (have had success on my Shop page though). 

I'd also like to change the mobile hamburger icon in the Shopping Cart to black and am having issues there too. 

I'd be grateful for any suggestions.

Site: https://bluebird-conch-c2nb.squarespace.com/

Password: 3ra(ysW3bz1+3

The gradient is in the site header settings, under style. Switch to "dynamic" from "gradient".

I think that the white hamburger icon may be because of the gradient, remove that in the settings and it should change, if not, let me know.

I have the gradient purposely applied to help the white navigation stand out from the imagery I'm using (which has made it more difficult on my end) and which is why I require some custom CSS to remove it just from the cart page (without disabling the 'gradient' header setting across the entire site.

Add this to Design > Custom CSS to remove gradient on Cart Page Header

body#cart .header-background-gradient {
    background-image: unset !important;
}