Update core/src/css/palettes/high-contrast-dark.scss

Co-authored-by: Brandy Smith <brandyscarney@users.noreply.github.com>

Author: gnbm

core/src/css/palettes/high-contrast-dark.scss

@@ -119,7 +119,7 @@ $lightest-text-color: $text-color;
     --ion-text-color-rgb: #{color-to-rgb-list($text-color)};
     --ion-item-background: #000000;
     --ion-card-background: #1c1c1d;
-    --ion-tab-bar-background-focused: #0b0b0b;
+    --ion-tab-bar-background-focused: #252525;
 
     /// Only the item borders should increase in contrast
     /// Borders for elements like toolbars should remain the same