cronet: disable defaults in tm-mainline-prod

This should have never been enabled in tm-mainline-prod, but was brought
in while fixing the automerger from aosp-master.

Test: TH
Merged-In: I5c00deb03c9c2718e139fb7639092419bf82a597
Change-Id: I395ef58b0f1af842cf3755a0a184d08a76b66538
1 file changed