Improve bitrate probing for the audio-only case.

webrtc/modules/pacing/alr_detector.cc

Index: webrtc/modules/pacing/alr_detector.cc
diff --git a/webrtc/modules/pacing/alr_detector.cc b/webrtc/modules/pacing/alr_detector.cc
index b31d4482bba37896bb7b0709d7e796d6e8c6eb53..9eeca2601228b8b36b9dc22f14ffe1d899f286c0 100644
--- a/webrtc/modules/pacing/alr_detector.cc
+++ b/webrtc/modules/pacing/alr_detector.cc
@@ -23,8 +23,8 @@ constexpr int kMeasurementPeriodMs = 500;
 // kAlrStartUsagePercent and ends when it raises above kAlrEndUsagePercent.
 // NOTE: This is intentionally conservative at the moment until BW adjustments
 // of application limited region is fine tuned.
-constexpr int kAlrStartUsagePercent = 30;
-constexpr int kAlrEndUsagePercent = 50;
+constexpr int kAlrStartUsagePercent = 60;
+constexpr int kAlrEndUsagePercent = 70;
 
 }  // namespace