Fix the icon name in Spectrum

switcherIconDark does not actually exist. Instead,
switcherIcon is the one that needs to be used.

Fixed: chromium:1179638
Change-Id: I130e2ca8d03e5efbc4cbbd49a6c719ef6dd1e1d7
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2703254
Auto-Submit: Alex Rudenko <alexrudenko@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>

front_end/color_picker/Spectrum.ts

@@ -426,8 +426,7 @@ export class Spectrum extends UI.Widget.VBox {
 
     function appendSwitcherIcon(parentElement: Element): void {
       const switcherIcon = new WebComponents.Icon.Icon();
-      switcherIcon
-          .data = {iconName: 'switcherIconDark', color: 'var(--color-text-primary)', width: '16px', height: '16px'};
+      switcherIcon.data = {iconName: 'switcherIcon', color: 'var(--color-text-primary)', width: '16px', height: '16px'};
       parentElement.appendChild(switcherIcon);
     }
   }