afdo: Remove -fprofile-sample-accurate flag

-fprofile-sample-accurate allows the compiler to de-optimize cold code
paths according to the profile. However we have a number of micro-
benchmarks that tests these paths and we often trigger regression
reports from those benchmarks.

Turning off the flag mitigates the issue at a cost of ~2MB increase in
system image size. But the more deterministic codegen could reduce the
differential OTA size.

Test: presubmit
Bug: 283235002
Change-Id: I1016f573f21a60223a97c64f5818f0e7e66e41e3