Revert "Notify first packet received after receptiveness change"

This reverts commit a14f6dc908f5e23c2b58062f5ae3bfbd7aec8502.

Reason for revert: Breaks downstream project

Original change's description:
> Notify first packet received after receptiveness change
>
> similar to NotifyFirstPacket but fires after changes to
> the receptiveness.
>
> No-IWYU: bot broken
> Bug: chromium:40821064
> Change-Id: I9fc9a229a13891dee2f286faadb8a53e54cd370d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/411380
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Reviewed-by: Henrik Boström <hbos@webrtc.org>
> Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
> Cr-Commit-Position: refs/heads/main@{#46158}

Bug: chromium:40821064
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I55df9cb803b48c98329cf5169dd4e75d6e9c06bf
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/424741
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/main@{#46163}