Make sidebar white (#22615)

frontend/src/metabase/nav/containers/MainNavbar/MainNavbar.styled.tsx

@@ -30,6 +30,7 @@ export const Sidebar = styled.aside<{ isOpen: boolean }>`
   flex-shrink: 0;
   align-items: center;
   padding: 0.5rem 0;
+  background-color: ${color("white")};
 
   overflow: auto;
   overflow-x: hidden;