Bug fix for dynamic island BG delta opacity

- Reported as an issue in Dynamic BG Color thread on Discord
- The delta was set to opacity = 50%, making it faded and hard to read
- This change removes the opacity modifier
- Discussion [here](https://discord.com/channels/1020905149037813862/1269507459416985630/1291837210441814151)

LiveActivity/LiveActivity.swift

@@ -159,7 +159,7 @@ struct LiveActivity: Widget {
 
     @ViewBuilder private func changeLabel(context: ActivityViewContext<LiveActivityAttributes>) -> some View {
         if !context.state.change.isEmpty {
-            Text(context.state.change).foregroundStyle(.primary.opacity(0.5)).font(.headline)
+            Text(context.state.change).foregroundStyle(.primary).font(.headline)
                 .strikethrough(context.isStale, pattern: .solid, color: .red.opacity(0.6))
         } else {
             Text("--")