Revert of FrameBuffer for the new jitter buffer. (patchset #9 id:160001 of https://codereview.webrtc.org/1969403007/ )

Reason for revert:
Two tests added by this CL failed in Win DrMemory Full:
 TestFrameBuffer2.OneLayerStreamReordered - TestFrameBuffer2.WaitForFrame

See the link here:
https://build.chromium.org/p/client.webrtc/waterfall?builder=Win%20DrMemory%20Full

Original issue's description:
> FrameBuffer for the new jitter buffer.
>
> BUG=webrtc:5514
> R=danilchap@webrtc.org, mflodman@webrtc.org
>
> Committed: https://crrev.com/a376e70cf9d0df3c35d53533b454da542661775b
> Cr-Commit-Position: refs/heads/master@{#12798}

TBR=mflodman@webrtc.org,danilchap@webrtc.org,philipel@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5514

Review-Url: https://codereview.webrtc.org/1991513004
Cr-Commit-Position: refs/heads/master@{#12800}

webrtc/modules/video_coding/frame_object.h

@@ -31,7 +31,6 @@ class FrameObject {
   // have to be constructed from the header data relevant to that codec.
   uint16_t picture_id;
   uint8_t spatial_layer;
-  uint32_t timestamp;
 
   size_t num_references;
   uint16_t references[kMaxFrameReferences];