Adding comment regarding the disabling the flaky test VolumeTest.ManualRequiresMicrophoneCanSetMicrophoneVolumeWithAgcOff

NOTRY=True
TBR=henrika@webrtc.org
BUG=webrtc:6206

Review-Url: https://codereview.webrtc.org/2247733002
Cr-Original-Commit-Position: refs/heads/master@{#13749}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 96dbc8f4b42cb9d3f7c5bf7e9dca1fa3925cff6e
1 file changed