Delete deprecated and unused method VideoFrame::SetTimeStamp.
Delete deprecated and unused method VideoFrame::SetTimeStamp.

BUG=webrtc:5682

Review-Url: https://codereview.webrtc.org/2283763002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#13948}

TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc