Remove anonymous namespace around ABSL_FLAG.
Remove anonymous namespace around ABSL_FLAG.

TBR=tommi@webrtc.org

No-Try: True
Bug: webrtc:10616
Change-Id: I371801b1c32fbf5103ad40b56e6dd396b53a9007
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/146201
Commit-Queue: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
Reviewed-by: Mirko Bonadei <d2c43c210eae6feef04f53bae50885e8152edcca@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28607}

ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc