Removed bitrate_controller.h file reference from gn file.
Removed bitrate_controller.h file reference from gn file.

BitrateAllocator was moved from BitrateController logic to Call in
https://chromium.googlesource.com/external/webrtc/+/0e7e259ebd69993bb5670a991f43aa1b06c9bf9e

BUG=None
NOTRY=True

Review-Url: https://codereview.webrtc.org/2342913004
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#14267}

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