PrefixSearch: Remove unnecessary wfSuppressWarnings()

It was added in 4492854f (r68563), where the code this was suppressing
warnings for was something rather different. It doesn't seem necessary now.

Change-Id: Ia501afd1244b94563fe52294945798963f8db1a9
Merge "PrefixSearch: Remove unnecessary wfSuppressWarnings()"