Revert "Use GetTimestamp in encoded frame clone functions."

This reverts commit 8acefd4f5076e0c371f9b891e4bfcf477af13929.

Reason for revert: Upstream fixed.

Original change's description:
> Use GetTimestamp in encoded frame clone functions.
>
> Mock frames in Chromium tests do not overload the new
> GetRtpTimestampInfo() and fail.
>
> Bug: chromium:524901718
> Change-Id: I67ce2478b1b096ed82e22d72c88d0bdd41848c5a
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/486860
> Commit-Queue: Guido Urdaneta <guidou@webrtc.org>
> Commit-Queue: Leonardo Evi <evil@chromium.org>
> Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
> Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#48122}

Bug: chromium:524901718
Change-Id: I0940d955c1078b3fb97f3f0e9769c93a4402a7f8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/487360
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Commit-Queue: Leonardo Evi <evil@chromium.org>
Cr-Commit-Position: refs/heads/main@{#48146}