Retune AGC2 input volume controller speech ratio threshold

Based on offline testing; needed to allow input volume adaptations
more frequently. Note that if the estimated speech level falls in
the target range, the recommended input volume won't change and
hence the new lower threshold won't necessarily increase the
number of adjustments.

Bug: webrtc:7494
Change-Id: Iabb501c188da238ea7b7137175bcfe09239c90a2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/291110
Reviewed-by: Hanna Silen <silen@webrtc.org>
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39161}
diff --git a/modules/audio_processing/agc2/input_volume_controller.h b/modules/audio_processing/agc2/input_volume_controller.h
index 40eae88..2140554 100644
--- a/modules/audio_processing/agc2/input_volume_controller.h
+++ b/modules/audio_processing/agc2/input_volume_controller.h
@@ -65,7 +65,7 @@
     float speech_probability_threshold = 0.7f;
     // Minimum speech frame ratio for volume updates to be allowed. Limited to
     // [0.0f, 1.0f].
-    float speech_ratio_threshold = 0.9f;
+    float speech_ratio_threshold = 0.6f;
   };
 
   // Ctor. `num_capture_channels` specifies the number of channels for the audio