Don't include packetization overhead in protection bitrate.
Don't include packetization overhead in protection bitrate.

If we do, the bitrate allocator will assume there can be a lot a FEC
and other things and bumps the max probing bitrate by 2x.
This caused a bunch of perf tests to change in a non-obvious way.

This is a follow-up to
https://webrtc-review.googlesource.com/c/src/+/115410

Bug: webrtc:10155, chromium:922396
Change-Id: I51d3611cb21d98a8fab1bfab2d8f167ed859696d
Reviewed-on: https://webrtc-review.googlesource.com/c/118043
Reviewed-by: Niels Moller <0057859e47d61d90529d0f66d9ef692cefedb46a@webrtc.org>
Commit-Queue: Erik Språng <3ab8c90c99d6dd7822e0fad803ab0211dd287ae5@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26319}
ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc