add flag set back on AOSP

this is a change to add the flag set back in AOSP test branch, flag enable check was removed in 24Q4, https://android-review.git.corp.google.com/c/platform/packages/modules/AdServices/+/3549820, but for go/ts-nextmilestones#no-regressions, this test also checks 24Q3 which still have that feature. set the flag to pass the check.

Flag: EXEMPT refactor
Bug: 407929947
Test: Presubmit
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:0e0d69f941a3a9bef53bdef733241a8be7d0ac6f)
(cherry picked from https://android-review.googlesource.com/q/commit:fc2275187ed5a8a13e6f350223a21cab8d5b5650)
Merged-In: I8a170c2ad861f8d9e388e80184f38737580cbc0a
Change-Id: I8a170c2ad861f8d9e388e80184f38737580cbc0a