fix(md): item border have correct contrast in dark mode

Author: liamdebeasi

core/src/css/palettes/dark.scss

@@ -142,7 +142,6 @@ $colors:  (
     --ion-background-color-rgb: 18, 18, 18;
     --ion-text-color: #ffffff;
     --ion-text-color-rgb: 255, 255, 255;
-    --ion-border-color: #222222;
     --ion-background-color-step-50: #1e1e1e;
     --ion-background-color-step-100: #2a2a2a;
     --ion-background-color-step-150: #363636;