Revert "BWE allocation strategy allows controlling of bitrate allocation with WEBRTC external logic."

This reverts commit 54d1da13a584680ae80a1f229291e5bb7e76e6e1.

Reason for revert: Breaking tests

Original change's description:
> BWE allocation strategy allows controlling of bitrate allocation with WEBRTC external logic.
> 
> This CL implements the main logic and IOS appRTC integration.
> 
> Unit tests and Android appRTC will be in separate CL.
> 
> Bug: webrtc:8243
> Change-Id: If8e5195294046a47316e9fade1b0dfec211155e1
> Reviewed-on: https://webrtc-review.googlesource.com/4860
> Commit-Queue: Alex Narest <alexnarest@webrtc.org>
> Reviewed-by: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20329}

TBR=deadbeef@webrtc.org,nisse@webrtc.org,stefan@webrtc.org,alexnarest@webrtc.org

Change-Id: I5be1da78f360f72be66f9d56dd6b88c1cc13e963
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8243
Reviewed-on: https://webrtc-review.googlesource.com/12560
Reviewed-by: Lu Liu <lliuu@webrtc.org>
Commit-Queue: Lu Liu <lliuu@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20330}

api/peerconnectioninterface.h

@@ -786,13 +786,6 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
   // to the provided value.
   virtual RTCError SetBitrate(const BitrateParameters& bitrate) = 0;
 
-  // Sets current strategy. If not set default WebRTC allocator will be used.
-  // May be changed during an active session. The strategy
-  // ownership is passed with std::unique_ptr
-  virtual void SetBitrateAllocationStrategy(
-      std::unique_ptr<rtc::BitrateAllocationStrategy>
-          bitrate_allocation_strategy) = 0;
-
   // Returns the current SignalingState.
   virtual SignalingState signaling_state() = 0;
   virtual IceConnectionState ice_connection_state() = 0;