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: refs/heads/master@{#14267}
diff --git a/webrtc/modules/bitrate_controller/BUILD.gn b/webrtc/modules/bitrate_controller/BUILD.gn
index 0440418..7f10c5d 100644
--- a/webrtc/modules/bitrate_controller/BUILD.gn
+++ b/webrtc/modules/bitrate_controller/BUILD.gn
@@ -12,7 +12,6 @@
   sources = [
     "bitrate_controller_impl.cc",
     "bitrate_controller_impl.h",
-    "include/bitrate_allocator.h",
     "include/bitrate_controller.h",
     "send_side_bandwidth_estimation.cc",
     "send_side_bandwidth_estimation.h",