[118] Move setting rtpTimestamp out of an incorrect feature check

This field should not be gated on RTCEncodedVideoFrameAdditionalMetadataEnabled. Its exposure is already
gated in the idl on the correct RTCEncodedFrameSetMetadata feature.

(cherry picked from commit 1022504)

Bug: 1487223
Change-Id: Ie8c91182bb610bcf315cfe8a83b1a8ddc4e7ad31
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4896897
Commit-Queue: Tony Herre <toprice@chromium.org>
Auto-Submit: Tony Herre <toprice@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Palak Agarwal <agpalak@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1202429}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4905404
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/branch-heads/5993@{#1083}
Cr-Branched-From: 5113507-refs/heads/main@{#1192594}

third_party/blink/renderer/modules/peerconnection/rtc_encoded_video_frame.cc

@@ -136,7 +136,6 @@ RTCEncodedVideoFrameMetadata* RTCEncodedVideoFrame::getMetadata() const {
     if (delegate_->CaptureTimeIdentifier()) {
       metadata->setCaptureTimestamp(delegate_->CaptureTimeIdentifier()->us());
     }
-    metadata->setRtpTimestamp(delegate_->RtpTimestamp());
   }
 
   const absl::optional<webrtc::VideoFrameMetadata> webrtc_metadata =
@@ -165,6 +164,7 @@ RTCEncodedVideoFrameMetadata* RTCEncodedVideoFrame::getMetadata() const {
   metadata->setHeight(webrtc_metadata->GetHeight());
   metadata->setSpatialIndex(webrtc_metadata->GetSpatialIndex());
   metadata->setTemporalIndex(webrtc_metadata->GetTemporalIndex());
+  metadata->setRtpTimestamp(delegate_->RtpTimestamp());
 
   return metadata;
 }