fix(theme) Fix the resize corner handles in the dark theme. (#6673)

- Changed the `canvasControlsSizeBoxShadowColor20` and
`canvasControlsSizeBoxShadowColor50` theme properties.

Author: seanparsons

editor/src/uuiui/styles/theme/dark.ts

@@ -138,8 +138,8 @@ const colorsWithOpacity = {
   whiteOpacity35: createUtopiColor('oklch(100% 0 0 /35%)'),
   grey65: createUtopiColor('oklch(65% 0 0)'),
   blackOpacity35: createUtopiColor('oklch(0% 0 0 / 35%)'),
-  canvasControlsSizeBoxShadowColor20: createUtopiColor('rgba(255,255,255,0.20)'),
-  canvasControlsSizeBoxShadowColor50: createUtopiColor('rgba(255,255,255,0.5)'),
+  canvasControlsSizeBoxShadowColor20: createUtopiColor('rgba(0,0,0,0.20)'),
+  canvasControlsSizeBoxShadowColor50: createUtopiColor('rgba(0,0,0,0.5)'),
   neutralInvertedBackground10: createUtopiColor('rgba(217, 220, 227, 0.1)'),
   neutralInvertedBackground20: createUtopiColor('rgba(217, 220, 227, 0.2)'),
   neutralInvertedBackground30: createUtopiColor('rgba(217, 220, 227, 0.3)'),