Fix TestLevelMonitoringHighBitrate test

The bitrate constrait was changed in f0b9ec1. Need to increase target
bitrate for the test to pass.

Change-Id: I56d6c656c9f58e46b953c3481534e9f7f1671da9
diff --git a/test/level_test.cc b/test/level_test.cc
index 29b9245..03f5113 100644
--- a/test/level_test.cc
+++ b/test/level_test.cc
@@ -129,7 +129,7 @@
     libaom_test::I420VideoSource video("hantro_collage_w352h288.yuv", 352, 288,
                                        30, 1, 0, 40);
     target_level_ = kLevelKeepStats;
-    cfg_.rc_target_bitrate = 3000;
+    cfg_.rc_target_bitrate = 4000;
     ASSERT_NO_FATAL_FAILURE(RunLoop(&video));
     ASSERT_EQ(level_[0], 1);
   }