Cleanup WebRTC-Vp9DependencyDescriptor field trial

Bug: chromium:1178444
Change-Id: Ie2ec796e207fa427fdbe00c8ea41a6b4fefea155
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/235374
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Commit-Queue: Emil Lundmark <lndmrk@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35241}

call/rtp_payload_params.cc

diff --git a/call/rtp_payload_params.cc b/call/rtp_payload_params.cc
index 3f98a58..53a4cca 100644
--- a/call/rtp_payload_params.cc
+++ b/call/rtp_payload_params.cc
@@ -131,10 +131,7 @@
     : ssrc_(ssrc),
       generic_picture_id_experiment_(
           absl::StartsWith(trials.Lookup("WebRTC-GenericPictureId"),
-                           "Enabled")),
-      simulate_generic_vp9_(
-          !absl::StartsWith(trials.Lookup("WebRTC-Vp9DependencyDescriptor"),
-                            "Disabled")) {
+                           "Enabled")) {
   for (auto& spatial_layer : last_shared_frame_id_)
     spatial_layer.fill(-1);
 
@@ -281,7 +278,7 @@
       }
       return;
     case VideoCodecType::kVideoCodecVP9:
-      if (simulate_generic_vp9_ && codec_specific_info != nullptr) {
+      if (codec_specific_info != nullptr) {
         Vp9ToGeneric(codec_specific_info->codecSpecific.VP9, frame_id,
                      *rtp_video_header);
       }