Fix the stereo support in IntelligibilityEnhancer

Review URL: https://codereview.webrtc.org/1729753003

Cr-Commit-Position: refs/heads/master@{#11795}
diff --git a/webrtc/modules/audio_processing/intelligibility/intelligibility_utils.h b/webrtc/modules/audio_processing/intelligibility/intelligibility_utils.h
index 3805a0c..11b9e49 100644
--- a/webrtc/modules/audio_processing/intelligibility/intelligibility_utils.h
+++ b/webrtc/modules/audio_processing/intelligibility/intelligibility_utils.h
@@ -12,7 +12,6 @@
 #define WEBRTC_MODULES_AUDIO_PROCESSING_INTELLIGIBILITY_INTELLIGIBILITY_UTILS_H_
 
 #include <complex>
-#include <memory>
 #include <vector>
 
 namespace webrtc {
@@ -55,13 +54,13 @@
              std::complex<float>* out_block);
 
   // Return the current target gain set. Modify this array to set the targets.
-  float* target() const { return target_.get(); }
+  float* target() { return target_.data(); }
 
  private:
   const size_t num_freqs_;
   const float relative_change_limit_;
-  std::unique_ptr<float[]> target_;
-  std::unique_ptr<float[]> current_;
+  std::vector<float> target_;
+  std::vector<float> current_;
 };
 
 }  // namespace intelligibility