Fix: update successColor in Sepia theme to Green700 (#6506)

Author: cooltey

app/src/main/java/org/wikipedia/compose/theme/WikipediaColor.kt

@@ -111,7 +111,7 @@ val SepiaColors = WikipediaColor(
     secondaryColor = ComposeColors.Gray600,
     borderColor = ComposeColors.Beige400,
     progressiveColor = ComposeColors.Blue600,
-    successColor = ComposeColors.Gray700,
+    successColor = ComposeColors.Green700,
     destructiveColor = ComposeColors.Red700,
     warningColor = ComposeColors.Yellow700,
     highlightColor = ComposeColors.Yellow500,