Revert of -enable UBsan on AGC. (patchset #1 id:1 of https://codereview.webrtc.org/2063643003/ )

Reason for revert:
Breaks downstream code import.

Original issue's description:
> Reland of Re-enable UBsan on AGC.
>
> patchset #8 id:300001 of https://codereview.webrtc.org/2003623003/
>
> This reverts commit 2b9423f7a18145255deb93f2505a4fd1c3fa9ad7.
>
> BUG=webrtc:5530
> TBR=peah@webrtc.org, kjellander@webrtc.org
>
> Committed: https://crrev.com/b1963b403f8e9258c35a02d2622da254cbb90c51
> Cr-Commit-Position: refs/heads/master@{#13132}

TBR=henrik.lundin@webrtc.org,minyue@webrtc.org
BUG=webrtc:5530
NOTRY=true

Review-Url: https://codereview.webrtc.org/2078433003
Cr-Original-Commit-Position: refs/heads/master@{#13169}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 4867ca2689d6576a750180b8f8e6bd9a9e23056f
3 files changed