Revert "[InsertableStreams] Fix simulcast: set frame transformer for all streams"

This reverts commit d926cf63b57128d9ea9a8d1054f853b4fe82e6dd.

Reason for revert: Breaks simulcast testing in Canary, to be relanded once the chrome part of the fix is landed as well.

Original change's description:
> [InsertableStreams] Fix simulcast: set frame transformer for all streams
> 
> The transformer was previously moved into the config of the first stream
> which resulted in incorrect behavior for simulcast. Use the transformer
> in all the streams.
> 
> Bug: chromium:1065838
> Change-Id: Iea340443da8cd4de32953bb24d3e6a07a275ae2a
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173026
> Reviewed-by: Magnus Flodman <mflodman@webrtc.org>
> Commit-Queue: Marina Ciocea <marinaciocea@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31018}

TBR=mflodman@webrtc.org,marinaciocea@webrtc.org

Change-Id: Ib0f869ae617329eb2532b613741b6050bd3ba2a3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1065838
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173181
Reviewed-by: Marina Ciocea <marinaciocea@webrtc.org>
Commit-Queue: Marina Ciocea <marinaciocea@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31033}

call/rtp_video_sender.cc

diff --git a/call/rtp_video_sender.cc b/call/rtp_video_sender.cc
index 3a6a27c..cb32085 100644
--- a/call/rtp_video_sender.cc
+++ b/call/rtp_video_sender.cc
@@ -273,7 +273,7 @@
         rtp_config.ulpfec.red_payload_type != -1) {
       video_config.red_payload_type = rtp_config.ulpfec.red_payload_type;
     }
-    video_config.frame_transformer = frame_transformer;
+    video_config.frame_transformer = std::move(frame_transformer);
     auto sender_video = std::make_unique<RTPSenderVideo>(video_config);
     rtp_streams.emplace_back(std::move(rtp_rtcp), std::move(sender_video),
                              std::move(fec_generator));