Remove release fence flags

ce_fence_promise and screenshot_fence_preservation flags
have been out for several releases. They can be deleted,
along with any obsolete code related to the flag removal.

Bug: 351894825
Test: atest SurfaceFlinger_test
Flag: EXEMPT flag removal
Change-Id: Iba6166358c96ff6cfe5c64b68640fcd992c4089f