Remove flag fixAvatarCrossUserLeak

Remove flag since this is a security fix and missing the flag on security branch is causing build failure.

Bug: 341688848
Test: N/A
Flag: EXEMPT bugfix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:2ab1084a748a2303289624e6063d2c60d10ec922)
Merged-In: I7d92e0bdb750a5e0a81e9bfd03ea50686c82f6e0
Change-Id: I7d92e0bdb750a5e0a81e9bfd03ea50686c82f6e0