Update AVG_BW_TO_LOW_BW_RATIO

Reduce AVG_BW_TO_LOW_BW_RATIO from 4 to 8/3 to improve bandwidth estimator
accuracy especially in case of web traffic.

Test: manual
Bug: 183995852
Change-Id: Id84976e8be88e632d7c2089f3190922cf84746eb
2 files changed