Remove content_features.h inclusion from media_stream_constraints_util_audio.cc

Driven by CL that paves the way to Onion souping
media_stream_constraints_util_audio.cc.

This effort is part of phase 4.6.3 in the design doc [1].

[1] https://docs.google.com/document/d/1rHJGi1U72qZsOGIctIf7GKRaY8d7BgtVW8MaMYumzYY/

BUG=704136
R=guidou@chromium.org

Change-Id: I944851ad08fd2d8fa4d2e1d3550f4ebef7e81f37
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704361
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678040}

content/renderer/media/stream/media_stream_constraints_util_audio.cc

@@ -12,7 +12,6 @@
 
 #include "base/strings/string_number_conversions.h"
 #include "build/build_config.h"
-#include "content/public/common/content_features.h"
 #include "content/renderer/media/stream/processed_local_audio_source.h"
 #include "media/audio/audio_features.h"
 #include "media/base/audio_parameters.h"