Revert "Call OnReceivedOverhead after audio network adaptor is created."

This reverts commit a135557b3c7ffa4fb1710d2d907c3cb86c5d5913.

Reason for revert: Suspected downstream breakage

Original change's description:
> Call OnReceivedOverhead after audio network adaptor is created.
> 
> This prevents ending up in a state where audio network adaptor never
> receives the current packet overhead and therefore doesn't work.
> 
> Bug: chromium:1086942
> Change-Id: I8ee2ffbb7741b342b3ec93fc89f2859a146f4ba7
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181583
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Per Åhgren <peah@webrtc.org>
> Commit-Queue: Jakob Ivarsson <jakobi@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31951}

TBR=peah@webrtc.org,sprang@webrtc.org,jakobi@webrtc.org

Change-Id: I96a92f82f0431457d649cc7feb253f0e026eeada
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1086942
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181885
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31954}

test/mock_audio_encoder.h

@@ -48,10 +48,6 @@ class MockAudioEncoder : public AudioEncoder {
               OnReceivedUplinkPacketLossFraction,
               (float uplink_packet_loss_fraction),
               (override));
-  MOCK_METHOD(void,
-              OnReceivedOverhead,
-              (size_t overhead_bytes_per_packet),
-              (override));
 
   MOCK_METHOD(bool,
               EnableAudioNetworkAdaptor,