fix(following): 减淡继续观看封面遮罩亮度

lib/pages/following/widgets/continue_watching_banner.dart

@@ -49,8 +49,8 @@ class ContinueWatchingBanner extends StatelessWidget {
                   begin: Alignment.centerLeft,
                   end: Alignment.centerRight,
                   colors: [
-                    Color(0xCC000000),
+                    Color(0x80000000),
-                    Color(0x99000000),
+                    Color(0x33000000),
                     Color(0x00000000),
                   ],
                   stops: [0, 0.45, 1],