Revert "Remove packets from RtpPacketHistory if acked via TransportFeedback"

This reverts commit 3890e99b705065dbc60e6d16932d8584bd67200d.

Reason for revert: Seems to be causing unexpected perf regressions.

Original change's description:
> Remove packets from RtpPacketHistory if acked via TransportFeedback
> 
> If the receiver has indicated that a packet has been received, via a
> TransportFeedback RTCP message, it is safe to remove it from the
> RtpPacketHistory as we can be sure it won't be needed anymore.
> This will reduce memory usage, reduce the risk of overflow in the
> history at very high bitrates, and hopefully make payload based padding
> a little more useful.
> 
> Bug: webrtc:8975
> Change-Id: I703a353252943f63d7d6edda68f03bc482633fd6
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/133028
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Sebastian Jansson <srte@webrtc.org>
> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#27745}

TBR=danilchap@webrtc.org,sprang@webrtc.org,srte@webrtc.org

Change-Id: I68ea6cf5c8988d4b625f14a1a9bc556c06a39368
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8975
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/134161
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27752}

modules/rtp_rtcp/include/rtp_rtcp.h

@@ -275,11 +275,6 @@ class RtpRtcp : public Module, public RtcpFeedbackSenderInterface {
   virtual StreamDataCountersCallback* GetSendChannelRtpStatisticsCallback()
       const = 0;
 
-  // Returns a pointer to an observer that handles information about packets
-  // that have been received by the remote end, or nullptr if not applicable.
-  virtual AcknowledgedPacketsObserver* GetAcknowledgedPacketsObserver()
-      const = 0;
-
   // **************************************************************************
   // RTCP
   // **************************************************************************