Revert webrtc/build/mb_config.pyl accidental change
Revert webrtc/build/mb_config.pyl accidental change

In https://codereview.webrtc.org/2320043002/ a mb_config.pyl
change that belonged to https://codereview.webrtc.org/2325063002/
accidentally was included.
This reverts it.

TBR=ehmaldonado@webrtc.org
BUG=

Review URL: https://codereview.webrtc.org/2319123005 .

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#14164}

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