Reduce duration of benchmark to avoid timeout (#51214)

dev/benchmarks/macrobenchmarks/test_driver/animated_placeholder_perf_test.dart

@@ -11,6 +11,6 @@ void main() {
     'animated_placeholder_perf',
     kAnimatedPlaceholderRouteName,
     pageDelay: const Duration(seconds: 1),
-    duration: const Duration(seconds: 15),
+    duration: const Duration(seconds: 5),
   );
 }