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/video_coding.gypi

@@ -32,7 +32,6 @@
         'encoded_frame.h',
         'fec_tables_xor.h',
         'frame_buffer.h',
-        'frame_buffer2.h',
         'frame_object.h',
         'rtp_frame_reference_finder.h',
         'generic_decoder.h',
@@ -63,7 +62,6 @@
         'decoding_state.cc',
         'encoded_frame.cc',
         'frame_buffer.cc',
-        'frame_buffer2.cc',
         'frame_object.cc',
         'rtp_frame_reference_finder.cc',
         'generic_decoder.cc',